[27619] in resnet
Re: SOHO WiFi routers and residential networking
daemon@ATHENA.MIT.EDU (Chris Webster)
Thu May 3 15:30:21 2012
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Date: Thu, 3 May 2012 15:29:44 -0400
Reply-To: Resnet Forum <RESNET-L@listserv.nd.edu>
From: Chris Webster <chris.webster@NCSU.EDU>
To: RESNET-L@listserv.nd.edu
In-Reply-To: <D0A43E8CC19B144398DFEC438095CB180E39DE0EB2@EXCMS.msu.montana.edu>
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It's possible to have multiple subnets in a single VLAN. We have a few
VLANs here that have multiple /24s assigned to them.
Running out of addresses will likely manifest as machines sometimes getting
an IP address and sometimes not, depending on your DHCP implementation and
lease times. It will be fairly obvious, but only if you're already
entertaining that as an idea. Otherwise it sounds absolutely ludicrous.
-Chris
On Thu, May 3, 2012 at 2:51 PM, Crowe, Sheila <sheila@montana.edu> wrote:
> Based on the correct definition of /24, our subnets are not larger than
> 256 IP addresses. Given that, I=92m wondering how we were ever able to j=
ust
> use one subnet? We have well over than 300 devices connected at one time
> in a single subnet. Reckon they=92re counting on not everyone being
> connected at the same time, but that=92s pretty iffy in our larger dorms
> (~300 residents there). In Family Housing, at peak times of the year, we
> have more than 500 users. Good Lord. If not enough IP space is the
> problem, I might open a vein. (My sense of humor is sometimes
> inappropriate). ****
>
> ** **
>
> Adam, these floods continue but are much fewer in number per day than the=
y
> used to be. I don't have a record of a packet capture at hand (I will as=
k
> for one), but Central IT uses =93Cacti monitoring of switch ports, with t=
he
> Threshold plugin configured to detect unicast packet rates well above
> normal on one (or more) interfaces.=94 Central IT is triggering on one of=
our
> fiber uplinks when the unicast packet rate exceeds 50,000 packets/second.
> I get a report every time this happens=85used to happen hundreds of times=
per
> day is now down to about 1-2 per day since our network guy has begun
> configuring those fiber ports with flood blocking.****
>
> ** **
>
> ~Sheila Crowe****
>
> ** **
>
> *From:* Resnet Forum [mailto:RESNET-L@LISTSERV.ND.EDU] *On Behalf Of *Rya=
n
> Dorman
> *Sent:* Thursday, May 03, 2012 12:20 PM
>
> *To:* RESNET-L@LISTSERV.ND.EDU
> *Subject:* Re: SOHO WiFi routers and residential networking****
>
> ** **
>
> Yep, happy to help with staring at captures.. its far more interesting
> than =93Strategy=94 whatever that meansJ****
>
> ** **
>
> As a general rule ( I say *general* I know there are exceptions, styles
> and other such that engineers use for IPAM) a /24 is the largest size
> network you should put end user PC=92s on. Especially given the chatty
> nature of Mac multicast/rendezvoux traffic, MS broadcast traffic etc etc =
it
> can result in a single packet being responded to by 100=92s of machines t=
hat
> it was not ultimately destined for=85. ****
>
> ** **
>
> ** **
>
> -rd****
>
> ** **
>
> *From:* Resnet Forum [mailto:RESNET-L@LISTSERV.ND.EDU] *On Behalf Of *Chr=
is
> Webster
> *Sent:* Thursday, May 03, 2012 11:04 AM
> *To:* RESNET-L@LISTSERV.ND.EDU
> *Subject:* Re: SOHO WiFi routers and residential networking****
>
> ** **
>
> Packet captures are almost always useful in identifying problems that
> can't be explained simply based on the symptoms (which it's why it's one =
of
> the first things network people look for). I'm happy to take a look at an=
y
> captures you have, with the caveat that the problem might be totally over
> my head.****
>
> ** **
>
> /24 is CIDR notation meaning a block of 256 IP addresses. Wikipedia link
> is the best I can do right now... I'll see if I can come up with a better
> explanatory article later:
> http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing#IPv4_CIDR_blo=
cks
> ****
>
>
> -Chris ****
>
> ** **
>
> On Thu, May 3, 2012 at 1:49 PM, Crowe, Sheila <sheila@montana.edu> wrote:=
*
> ***
>
> I'm sure that we have done packet captures, Adam...would it help to see
> those?
>
> Ryan, I'm not sure what you mean by subnets bigger than "/24." (I'm gonn=
a
> read the Eric Leahy paper at lunch). I'm learning a little about
> networking along the way, aren't I?
>
> My plan for the responses from the RESNET-L is to combine the suggestions
> and questions and present them to the network guy for analysis and answer=
s.
>
> Keep them coming! And thank you very much for sharing your expertise wit=
h
> me.****
>
>
> Sheila Crowe
> Montana State University****
>
> -----Original Message-----
> From: Resnet Forum [mailto:RESNET-L@LISTSERV.ND.EDU] On Behalf Of Brock,
> Adam
> Sent: Wednesday, May 02, 2012 9:24 PM
> To: RESNET-L@LISTSERV.ND.EDU
> Subject: Re: SOHO WiFi routers and residential networking****
>
> Also, did anyone try getting a packet capture of the unicast traffic, or
> was that just a theory?
> Sent from my Brockberry.
> ________________________________
> From: Ryan Dorman <Ryan.Dorman@blackboard.com>
> Sender: Resnet Forum <RESNET-L@LISTSERV.ND.EDU>
> Date: Wed, 2 May 2012 21:33:01 -0500
> To: RESNET-L@LISTSERV.ND.EDU<RESNET-L@LISTSERV.ND.EDU>
> ReplyTo: Resnet Forum <RESNET-L@LISTSERV.ND.EDU>
> Subject: Re: [RESNET-L] SOHO WiFi routers and residential networking
>
> My questions, slightly re-phrased:
>
> 1. For those of you who have a similar network, do you utilize
> either Storm Control or flood blocking? Why do you use one rather than t=
he
> other?****
>
> a. We used storm control in the dorms back in my day (ha ha ha)...
> it was one of our bandaid procedures for sasser/blaster (hence why I did
> not describe it as the good old days). It has advantage of dealing with
> multiple types of traffic, not just Unicast.****
>
>
> b. This is a good article explaining the differences
> http://ericleahy.com/?p=3D611
>
>
>
> 2. Do you use some other measure to deal with unicast packet floods=
?
>
> a. No
>
>
> 3. Considering the physical environment (single wired jacks), what
> do you feel is best practice when it comes to stopping unicast packet
> floods?
>
> a. There are a couple things I would look at here more from a desig=
n
> perspective then a flood protection angle
>
> i. How
> big are your subnets? If they are huge (bigger then /24) you're going to
> start running up against broadcast issues.
>
> ii. Have
> you considered Private VLAN's? Might help limit outages to a smaller gro=
up
> of people
>
> iii. Do
> you limit the number of MAC addresses on a single port?****
>
> It surprises me that you are seeing unicast flooding like this.. in campu=
s
> environments, and even in datacenters I have found that that is relativel=
y
> rare. Granted, I don't work in in reshalls anymore and the nature of tha=
t
> traffic is different then here in sell-out world :) but I'd be interested
> to see traces of who is flooding who and from what process etc etc...****
>
>
> Ryan Dorman
> Director, Enterprise Technology Strategy Blackboard Inc.
>
> O: 202.463.4860 x2618
> M: 202.370.7889
>
> From: Resnet Forum [mailto:RESNET-L@LISTSERV.ND.EDU] On Behalf Of Crowe,
> Sheila
> Sent: Tuesday, May 01, 2012 2:15 PM
> To: RESNET-L@LISTSERV.ND.EDU
> Subject: Re: SOHO WiFi routers and residential networking
>
> Thank you to Rand, Bruce and my hero, Adam Brock.****
>
> A bit more detailed information to help all the Cisco network guru types
> help me. To recap...****
>
>
> We have 2 housing areas: residence halls and family and graduate
> apartments. Both areas have Cisco 2960 layer 2 switches and Cisco 3750
> fiber switches. In the residence halls we have one wired port per pillow
> and almost ubiquitous wireless coverage via Aruba APs and a single
> controller. ResNet is charged as part of the room and board in the
> residence halls.
>
> We don't provide wireless coverage in family and graduate housing. Our
> family housing area was wired about 13 years ago and provided only one
> wired jack per apartment; because of that, virtually every customer in
> family housing uses a soho wireless router. Prior to our upgrade in June=
,
> we were using 3Com fiber switches and Cisco 2960 layer 2 switches, When w=
e
> upgraded this section of our network (from 3Com fiber switches to Cisco
> 3750s), we immediately had a BIG problem with our network dropping in
> family housing; no problems in the res halls. Backwards soho routers wer=
e
> not the problem because we use DHCP snooping. Prior to the upgrade, our
> network ran like a scalded cat in FGH. It was ultimately decided that th=
e
> problem was caused by the larger concentration of SOHO wireless routers i=
n
> that area producing unicast packet floods. Our team has discovered that
> Cisco switches have a feature called flood blocking that will block unica=
st
> and multicast floods at the switchpor!
> t level. We are deploying this slowly. I am told that it is NOT Cisco'=
s
> Storm Control.
>
> My questions, slightly re-phrased:
>
> 1. For those of you who have a similar network, do you utilize
> either Storm Control or flood blocking? Why do you use one rather than t=
he
> other?
>
>
> 2. Do you use some other measure to deal with unicast packet floods=
?
>
>
> 3. Considering the physical environment (single wired jacks), what
> do you feel is best practice when it comes to stopping unicast packet
> floods?
>
>
> If you need more detail from me, please ask. Any information or feedback
> is appreciated. If you prefer, please feel free to contact me off-list.
>
> Thank you!
> Sheila Crowe
> MSU ResNet
> sheila@montana.edu<mailto:sheila@montana.edu>
>
>
> From: Resnet Forum [mailto:RESNET-L@LISTSERV.ND.EDU]<mailto:[mailto:
> RESNET-L@LISTSERV.ND.EDU]> On Behalf Of Osborne, Bruce W
> Sent: Tuesday, May 01, 2012 5:48 AM
> To: RESNET-L@LISTSERV.ND.EDU<mailto:RESNET-L@LISTSERV.ND.EDU>
> Subject: Re: SOHO WiFi routers and residential networking
>
> That is only the port part of the configuration. There are some global
> settings too.
>
> Also, your switch uplink or the switch port with the DHCP server needs to
> be trusted for this to function correctly. The three processes used here
> are "ARP inspection", "DHCO snooping", and "IP source guard". The feature=
s
> can vary, depending on your model of switch.
>
> Here is one example of Cisco's documentation. This one is for 3550
> switches.
> http://www.cisco.com/en/US/docs/switches/lan/catalyst3550/software/releas=
e/12.2_25_see/configuration/guide/swdhcp82.html
>
>
> Bruce Osborne
> Network Engineer
> IT Network Services
>
> (434) 592-4229
>
> LIBERTY UNIVERSITY
> Training Champions for Christ since 1971
>
> From: Hall, Rand [mailto:hallr@MERRIMACK.EDU]<mailto:[mailto:
> hallr@MERRIMACK.EDU]>
> Sent: Monday, April 30, 2012 12:39 PM
> Subject: Re: SOHO WiFi routers and residential networking
>
> Sheila,
>
> Good luck blocking rogues. :-) Your best bet is to hold to your commitmen=
t
> to providing service to the jack. To that you can add some basic best
> practice suggestions to people who want to try using a wireless router or
> bridge (enable encryption, negotiate channel selection with neighbors, et=
c).
>
> Your network folks will want to turn on DHCP Snooping. Sometimes a
> resident will plug a router in "backwards" and offer up DHCP leases to
> their neighbors--not a pretty sight. If they are new to Cisco they might
> appreciate a sample interface config for some ideas. Feel free to share:
>
> switchport access vlan xx
> switchport mode access
> switchport protected
> switchport port-security maximum 6
> switchport port-security
> switchport port-security aging time 1
> switchport port-security violation restrict switchport port-security
> aging type inactivity ip arp inspection limit rate 15 burst interval 10
> storm-control broadcast level pps 50 10 storm-control multicast level p=
ps
> 50 10 spanning-tree portfast spanning-tree bpduguard enable ip verify
> source ip dhcp snooping limit rate 10
>
>
> Rand
>
> Rand P. Hall
> Director, Network Services askIT!
> Merrimack College
> 978-837-3532<tel:978-837-3532>
> rand.hall@merrimack.edu<mailto:rand.hall@merrimack.edu>
>
> If I had an hour to save the world, I would spend 59 minutes defining the
> problem and one minute finding solutions. - Einstein
>
> On Fri, Apr 27, 2012 at 1:48 PM, Crowe, Sheila <sheila@montana.edu<mailto=
:
> sheila@montana.edu>> wrote:
> In early March, I participated in a thread started by Jeannie Abney about
> what other schools' polices are for residents bringing personal wireless
> routers onto your network. I added some questions pertaining to single
> family apartments (vs. residence halls) and got some great feedback. I
> would like to take it a step further and ask some more questions based on
> the type of network that we have.
>
> We have a Cisco network, a core at the origin of the commodity internet
> pipe, and a subnet for each of our buildings (really areas). In the
> residence halls we have a large Aruba wireless network installed so that
> every building is blanketed for secure wireless internet access. In the
> residence halls, ResNet is charged out to every resident regardless of
> whether they use it or not.
>
> We do not provide ubiquitous wireless coverage in family housing because
> ResNet is an opt-in service. Additionally, our family housing area was
> wired about 13 years ago and only provided one wired jack per apartment. =
As
> I'm sure you can imagine, virtually every customer in family housing has =
a
> soho wireless router. When we upgraded this section of our network (from
> 3Com switches to Cisco), we immediately had a BIG problem with our networ=
k
> dropping constantly. It was ultimately decided that it was the SOHO
> wireless routers causing the problem; namely, unicast packet floods throu=
gh
> our Cisco switch ports. Only recently it was discovered that Cisco switch=
es
> have a feature that will block unicast and multicast floods. We are
> deploying this slowly.
>
> Now for the questions. For those of you who have a similar network, do yo=
u
> employ this Cisco feature or do you simply block all "rogue" wireless
> connections? Or do you have another measure in place to deal with the
> unicast packet floods? Also, do your network engineers consider this a
> stopgap measure ("band-aid") to deal with residences where you do not off=
er
> WiFi?
>
> Please do share all of the details about this issue (or non-issue) on you=
r
> network as you know them. And thanks a million!
>
> Sheila Crowe
> Montana State University ResNet
> 406.994.4230<tel:406.994.4230>
> 406.209.7243<tel:406.209.7243>
>
> P.S. I'm hoping to see all of you at the 2012 Student Technology
> Conference at Claremont Colleges!
>
> ___________________________________________________ You are subscribed to
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>
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> To subscribe, unsubscribe or search the archives, go to
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> To subscribe, unsubscribe or search the archives, go to
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> To subscribe, unsubscribe or search the archives, go to
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>
> This email and any attachments may contain confidential and proprietary
> information of Blackboard that is for the sole use of the intended
> recipient. If you are not the intended recipient, disclosure, copying,
> re-distribution or other use of any of this information is strictly
> prohibited. Please immediately notify the sender and delete this
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> To subscribe, unsubscribe or search the archives, go to
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> ___________________________________________________****
>
>
>
> ****
>
> ** **
>
> --
> Chris Webster
> Senior Technician
> OIT Walk-in Center
> North Carolina State University
>
> Ph: 919.513.2676
> Fax: 919.513.2945
> Email: chris.webster@ncsu.edu
> Web: http://go.ncsu.edu/wic/****
>
> ___________________________________________________ You are subscribed to
> the ResNet-L mailing list. ****
>
> To subscribe, unsubscribe or search the archives, go to
> http://LISTSERV.ND.EDU/archives/resnet-l.html____________________________=
_______________________
> ****
>
>
> This email and any attachments may contain confidential and proprietary
> information of Blackboard that is for the sole use of the intended
> recipient. If you are not the intended recipient, disclosure, copying,
> re-distribution or other use of any of this information is strictly
> prohibited. Please immediately notify the sender and delete this
> transmission if you received this email in error.****
>
> ___________________________________________________ You are subscribed to
> the ResNet-L mailing list. ****
>
> To subscribe, unsubscribe or search the archives, go to
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_______________________
> ****
> ___________________________________________________ You are subscribed to
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>
> To subscribe, unsubscribe or search the archives, go to
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>
--=20
Chris Webster
Senior Technician
OIT Walk-in Center
North Carolina State University
Ph: 919.513.2676
Fax: 919.513.2945
Email: chris.webster@ncsu.edu
Web: http://go.ncsu.edu/wic/
___________________________________________________
You are subscribed to the ResNet-L mailing list.
To subscribe, unsubscribe or search the archives,
go to http://LISTSERV.ND.EDU/archives/resnet-l.html
___________________________________________________
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Content-Type: text/html; charset=windows-1252
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It's possible to have multiple subnets in a single VLAN. We have a few =
VLANs here that have multiple /24s assigned to them.=A0<div><br></div><div>=
Running out of addresses will likely manifest as machines sometimes getting=
an IP address and sometimes not, depending on your DHCP implementation and=
lease times. It will be fairly obvious, but only if you're already ent=
ertaining that as an idea. Otherwise it sounds absolutely ludicrous.<div>
<br></div><div>-Chris<br><br><div class=3D"gmail_quote">On Thu, May 3, 2012=
at 2:51 PM, Crowe, Sheila <span dir=3D"ltr"><<a href=3D"mailto:sheila@m=
ontana.edu" target=3D"_blank">sheila@montana.edu</a>></span> wrote:<br><=
blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px=
#ccc solid;padding-left:1ex">
<div lang=3D"EN-US" link=3D"blue" vlink=3D"purple"><div><p>Based on the cor=
rect definition of /24, our subnets are not larger than 256 IP addresses.=
=A0 Given that, I=92m wondering how we were ever able to just use one subne=
t?=A0 We have well over than 300 devices connected at one time in a single =
subnet.=A0 Reckon they=92re counting on not everyone being connected at the=
same time, but that=92s pretty iffy in our larger dorms (~300 residents th=
ere).=A0 In Family Housing, at peak times of the year, we have more than 50=
0 users. =A0Good Lord.=A0 If not enough IP space is the problem, I might op=
en a vein.=A0 (My sense of humor is sometimes inappropriate).=A0 <u></u><u>=
</u></p>
<p><u></u>=A0<u></u></p><p>Adam, these floods continue but are much fewer i=
n number per day than they used to be.=A0 I don't have a record of a pa=
cket capture at hand (I will ask for one), but Central IT uses =93Cacti mon=
itoring of switch ports, with the Threshold plugin configured to detect uni=
cast packet rates well above normal on one (or more) interfaces.=94 Central=
IT is triggering on one of our fiber uplinks when the unicast packet rate =
exceeds 50,000 packets/second.=A0 I get a report every time this happens=85=
used to happen hundreds of times per day is now down to about 1-2 per day s=
ince our network guy has begun configuring those fiber ports with flood blo=
cking.<u></u><u></u></p>
<p class=3D"MsoNormal"><u></u>=A0<u></u></p><p>=A0 ~Sheila Crowe<u></u><u><=
/u></p><p class=3D"MsoNormal"><span style=3D"font-size:11.0pt;font-family:&=
quot;Calibri","sans-serif";color:#1f497d"><u></u>=A0<u></u><=
/span></p>
<div><div style=3D"border:none;border-top:solid #b5c4df 1.0pt;padding:3.0pt=
0in 0in 0in"><p class=3D"MsoNormal"><b><span style=3D"font-size:10.0pt;fon=
t-family:"Tahoma","sans-serif"">From:</span></b><span s=
tyle=3D"font-size:10.0pt;font-family:"Tahoma","sans-serif&qu=
ot;"> Resnet Forum [mailto:<a href=3D"mailto:RESNET-L@LISTSERV.ND.EDU" targ=
et=3D"_blank">RESNET-L@LISTSERV.ND.EDU</a>] <b>On Behalf Of </b>Ryan Dorman=
<br>
<b>Sent:</b> Thursday, May 03, 2012 12:20 PM</span></p><div><div class=3D"h=
5"><br><b>To:</b> <a href=3D"mailto:RESNET-L@LISTSERV.ND.EDU" target=3D"_bl=
ank">RESNET-L@LISTSERV.ND.EDU</a><br><b>Subject:</b> Re: SOHO WiFi routers =
and residential networking<u></u><u></u></div>
</div><p></p></div></div><div><div class=3D"h5"><p class=3D"MsoNormal"><u><=
/u>=A0<u></u></p><p class=3D"MsoNormal"><a name=3D"137140db93872bba__MailEn=
dCompose"><span style=3D"font-size:11.0pt;font-family:"Calibri",&=
quot;sans-serif";color:#1f497d">Yep, happy to help with staring at cap=
tures.. its far more interesting than =93Strategy=94 whatever that means</s=
pan></a><span style=3D"font-size:11.0pt;font-family:Wingdings;color:#1f497d=
">J</span><span style=3D"font-size:11.0pt;font-family:"Calibri",&=
quot;sans-serif";color:#1f497d"><u></u><u></u></span></p>
<p class=3D"MsoNormal"><span style=3D"font-size:11.0pt;font-family:"Ca=
libri","sans-serif";color:#1f497d"><u></u>=A0<u></u></span><=
/p><p class=3D"MsoNormal"><span style=3D"font-size:11.0pt;font-family:"=
;Calibri","sans-serif";color:#1f497d">As a general rule ( I =
say <b>general</b> I know there are exceptions, styles and other such that =
engineers use for IPAM) a /24 is the largest size network you should put en=
d user PC=92s on.=A0 Especially given the chatty nature of Mac multicast/re=
ndezvoux traffic, MS broadcast traffic etc etc it can result in a single pa=
cket being responded to by 100=92s of machines that it was not ultimately d=
estined for=85. <u></u><u></u></span></p>
<p class=3D"MsoNormal"><span style=3D"font-size:11.0pt;font-family:"Ca=
libri","sans-serif";color:#1f497d"><u></u>=A0<u></u></span><=
/p><p class=3D"MsoNormal"><span style=3D"font-size:11.0pt;font-family:"=
;Calibri","sans-serif";color:#1f497d"><u></u>=A0<u></u></spa=
n></p>
<p class=3D"MsoNormal"><span style=3D"font-size:11.0pt;font-family:"Ca=
libri","sans-serif";color:#1f497d">-rd<u></u><u></u></span><=
/p><p class=3D"MsoNormal"><span style=3D"font-size:11.0pt;font-family:"=
;Calibri","sans-serif";color:#1f497d"><u></u>=A0<u></u></spa=
n></p>
<p class=3D"MsoNormal"><b><span style=3D"font-size:10.0pt;font-family:"=
;Tahoma","sans-serif"">From:</span></b><span style=3D"font-s=
ize:10.0pt;font-family:"Tahoma","sans-serif""> Resnet F=
orum <a href=3D"mailto:[mailto:RESNET-L@LISTSERV.ND.EDU]" target=3D"_blank"=
>[mailto:RESNET-L@LISTSERV.ND.EDU]</a> <b>On Behalf Of </b>Chris Webster<br=
>
<b>Sent:</b> Thursday, May 03, 2012 11:04 AM<br><b>To:</b> <a href=3D"mailt=
o:RESNET-L@LISTSERV.ND.EDU" target=3D"_blank">RESNET-L@LISTSERV.ND.EDU</a><=
br><b>Subject:</b> Re: SOHO WiFi routers and residential networking<u></u><=
u></u></span></p>
<p class=3D"MsoNormal"><u></u>=A0<u></u></p><div><p class=3D"MsoNormal">Pac=
ket captures are almost always useful in identifying problems that can'=
t be explained simply based on the symptoms (which it's why it's on=
e of the first things network people look for). I'm happy to take a loo=
k at any captures you have, with the caveat that the problem might be total=
ly over my head.<u></u><u></u></p>
</div><div><p class=3D"MsoNormal"><u></u>=A0<u></u></p></div><p class=3D"Ms=
oNormal">/24 is CIDR notation meaning a block of 256 IP addresses.=A0Wikipe=
dia link is the best I can do right now... I'll see if I can come up wi=
th a better explanatory article later:=A0<a href=3D"http://en.wikipedia.org=
/wiki/Classless_Inter-Domain_Routing#IPv4_CIDR_blocks" target=3D"_blank">ht=
tp://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing#IPv4_CIDR_blocks<=
/a><u></u><u></u></p>
<div><p class=3D"MsoNormal"><br>-Chris=A0<u></u><u></u></p></div><div><p cl=
ass=3D"MsoNormal"><u></u>=A0<u></u></p><div><p class=3D"MsoNormal">On Thu, =
May 3, 2012 at 1:49 PM, Crowe, Sheila <<a href=3D"mailto:sheila@montana.=
edu" target=3D"_blank">sheila@montana.edu</a>> wrote:<u></u><u></u></p>
<p class=3D"MsoNormal">I'm sure that we have done packet captures, Adam=
...would it help to see those?<br><br>Ryan, I'm not sure what you mean =
by subnets bigger than "/24." =A0(I'm gonna read the Eric Lea=
hy paper at lunch). =A0I'm learning a little about networking along the=
way, aren't I?<br>
<br>My plan for the responses from the RESNET-L is to combine the suggestio=
ns and questions and present them to the network guy for analysis and answe=
rs.<br><br>Keep them coming! =A0And thank you very much for sharing your ex=
pertise with me.<u></u><u></u></p>
<div><p class=3D"MsoNormal" style=3D"margin-bottom:12.0pt"><br>Sheila Crowe=
<br>Montana State University<u></u><u></u></p></div><div><p class=3D"MsoNor=
mal" style=3D"margin-bottom:12.0pt">-----Original Message-----<br>From: Res=
net Forum [mailto:<a href=3D"mailto:RESNET-L@LISTSERV.ND.EDU" target=3D"_bl=
ank">RESNET-L@LISTSERV.ND.EDU</a>] On Behalf Of Brock, Adam<br>
Sent: Wednesday, May 02, 2012 9:24 PM<br>To: <a href=3D"mailto:RESNET-L@LIS=
TSERV.ND.EDU" target=3D"_blank">RESNET-L@LISTSERV.ND.EDU</a><br>Subject: Re=
: SOHO WiFi routers and residential networking<u></u><u></u></p></div><div>
<p class=3D"MsoNormal" style=3D"margin-bottom:12.0pt">Also, did anyone try =
getting a packet capture of the unicast traffic, or was that just a theory?=
<br>Sent from my Brockberry.<br>________________________________<br>From: R=
yan Dorman <<a href=3D"mailto:Ryan.Dorman@blackboard.com" target=3D"_bla=
nk">Ryan.Dorman@blackboard.com</a>><br>
Sender: Resnet Forum <<a href=3D"mailto:RESNET-L@LISTSERV.ND.EDU" target=
=3D"_blank">RESNET-L@LISTSERV.ND.EDU</a>><br>Date: Wed, 2 May 2012 21:33=
:01 -0500<br>To: <a href=3D"mailto:RESNET-L@LISTSERV.ND.EDU" target=3D"_bla=
nk">RESNET-L@LISTSERV.ND.EDU</a><<a href=3D"mailto:RESNET-L@LISTSERV.ND.=
EDU" target=3D"_blank">RESNET-L@LISTSERV.ND.EDU</a>><br>
ReplyTo: Resnet Forum <<a href=3D"mailto:RESNET-L@LISTSERV.ND.EDU" targe=
t=3D"_blank">RESNET-L@LISTSERV.ND.EDU</a>><br>Subject: Re: [RESNET-L] SO=
HO WiFi routers and residential networking<br><br>My questions, slightly re=
-phrased:<br>
<br>1. =A0 =A0 =A0 For those of you who have a similar network, do you util=
ize either Storm Control or flood blocking? =A0Why do you use one rather th=
an the other?<u></u><u></u></p></div><p class=3D"MsoNormal">a. =A0 =A0 =A0 =
We used storm control in the dorms back in my day (ha ha ha)... it was one =
of our bandaid procedures for sasser/blaster (hence why I did not describe =
it as the good old days). =A0It has advantage of dealing with multiple type=
s of traffic, not just Unicast.<u></u><u></u></p>
<div><p class=3D"MsoNormal" style=3D"margin-bottom:12.0pt"><br>b. =A0 =A0 =
=A0This is a good article explaining the differences <a href=3D"http://eric=
leahy.com/?p=3D611" target=3D"_blank">http://ericleahy.com/?p=3D611</a><br>=
<br><br><br>2. =A0 =A0 =A0 Do you use some other measure to deal with unica=
st packet floods?<br>
<br>a. =A0 =A0 =A0 No<br><br><br>3. =A0 =A0 =A0 Considering the physical en=
vironment (single wired jacks), what do you feel is best practice when it c=
omes to stopping unicast packet floods?<br><br>a. =A0 =A0 =A0 There are a c=
ouple things I would look at here more from a design perspective then a flo=
od protection angle<br>
<br>=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 i. =A0 =A0 =A0How big =
are your subnets? =A0If they are huge (bigger then /24) you're going to=
start running up against broadcast issues.<br><br>=A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
=A0 =A0 =A0 =A0 =A0 ii. =A0 =A0 =A0Have you considered Private VLAN's?=
=A0Might help limit outages to a smaller group of people<br>
<br>=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0iii. =A0 =A0 =A0Do you limi=
t the number of MAC addresses on a single port?<u></u><u></u></p></div><p c=
lass=3D"MsoNormal">It surprises me that you are seeing unicast flooding lik=
e this.. in campus environments, and even in datacenters I have found that =
that is relatively rare. =A0Granted, I don't work in in reshalls anymor=
e and the nature of that traffic is different then here in sell-out world :=
) but I'd be interested to see traces of who is flooding who and from w=
hat process etc etc...<u></u><u></u></p>
<div><p class=3D"MsoNormal" style=3D"margin-bottom:12.0pt"><br>Ryan Dorman<=
br>Director, Enterprise Technology Strategy Blackboard Inc.<br><br>O: <a hr=
ef=3D"tel:202.463.4860%20x2618" target=3D"_blank">202.463.4860 x2618</a><br=
>M: <a href=3D"tel:202.370.7889" target=3D"_blank">202.370.7889</a><br>
<br>From: Resnet Forum [mailto:<a href=3D"mailto:RESNET-L@LISTSERV.ND.EDU" =
target=3D"_blank">RESNET-L@LISTSERV.ND.EDU</a>] On Behalf Of Crowe, Sheila<=
br>Sent: Tuesday, May 01, 2012 2:15 PM<br>To: <a href=3D"mailto:RESNET-L@LI=
STSERV.ND.EDU" target=3D"_blank">RESNET-L@LISTSERV.ND.EDU</a><br>
Subject: Re: SOHO WiFi routers and residential networking<br><br>Thank you =
to Rand, Bruce and my hero, Adam Brock.<u></u><u></u></p></div><p class=3D"=
MsoNormal">A bit more detailed information to help all the Cisco network gu=
ru types help me. =A0To recap...<u></u><u></u></p>
<div><div><p class=3D"MsoNormal"><br>We have 2 housing areas: =A0residence =
halls and family and graduate apartments. =A0Both areas have Cisco 2960 lay=
er 2 switches and Cisco 3750 fiber switches. =A0In the residence halls we h=
ave one wired port per pillow and almost ubiquitous wireless coverage via A=
ruba APs and a single controller. =A0ResNet is charged as part of the room =
and board in the residence halls.<br>
<br>We don't provide wireless coverage in family and graduate housing. =
=A0Our family housing area was wired about 13 years ago and provided only o=
ne wired jack per apartment; because of that, virtually every customer in f=
amily housing uses a soho wireless router. =A0Prior to our upgrade in June,=
we were using 3Com fiber switches and Cisco 2960 layer 2 switches, When we=
upgraded this section of our network (from 3Com fiber switches to Cisco 37=
50s), we immediately had a BIG problem with our network dropping in family =
housing; no problems in the res halls. =A0Backwards soho routers were not t=
he problem because we use DHCP snooping. Prior to the upgrade, our network =
ran like a scalded cat in FGH. =A0It was ultimately decided that the proble=
m was caused by the larger concentration of SOHO wireless routers in that a=
rea producing unicast packet floods. =A0Our team has discovered that Cisco =
switches have a feature called flood blocking that will block unicast and m=
ulticast floods at the switchpor!<br>
=A0t level. =A0We are deploying this slowly. =A0I am told that it is NOT Ci=
sco's Storm Control.<br><br>My questions, slightly re-phrased:<br><br>1=
. =A0 =A0 =A0 For those of you who have a similar network, do you utilize e=
ither Storm Control or flood blocking? =A0Why do you use one rather than th=
e other?<br>
<br><br>2. =A0 =A0 =A0 Do you use some other measure to deal with unicast p=
acket floods?<br><br><br>3. =A0 =A0 =A0 Considering the physical environmen=
t (single wired jacks), what do you feel is best practice when it comes to =
stopping unicast packet floods?<br>
<br><br>If you need more detail from me, please ask. =A0Any information or =
feedback is appreciated. =A0If you prefer, please feel free to contact me o=
ff-list.<br><br>Thank you!<br>Sheila Crowe<br>MSU ResNet<br><a href=3D"mail=
to:sheila@montana.edu" target=3D"_blank">sheila@montana.edu</a><mailto:<=
a href=3D"mailto:sheila@montana.edu" target=3D"_blank">sheila@montana.edu</=
a>><br>
<br><br>From: Resnet Forum [mailto:<a href=3D"mailto:RESNET-L@LISTSERV.ND.E=
DU" target=3D"_blank">RESNET-L@LISTSERV.ND.EDU</a>]<mailto:[mailto:<a hr=
ef=3D"mailto:RESNET-L@LISTSERV.ND.EDU" target=3D"_blank">RESNET-L@LISTSERV.=
ND.EDU</a>]> On Behalf Of Osborne, Bruce W<br>
Sent: Tuesday, May 01, 2012 5:48 AM<br>To: <a href=3D"mailto:RESNET-L@LISTS=
ERV.ND.EDU" target=3D"_blank">RESNET-L@LISTSERV.ND.EDU</a><mailto:<a hre=
f=3D"mailto:RESNET-L@LISTSERV.ND.EDU" target=3D"_blank">RESNET-L@LISTSERV.N=
D.EDU</a>><br>
Subject: Re: SOHO WiFi routers and residential networking<br><br>That is on=
ly the port part of the configuration. There are some global settings too.<=
br><br>Also, your switch uplink or the switch port with the DHCP server nee=
ds to be trusted for this to function correctly. The three processes used h=
ere are "ARP inspection", "DHCO snooping", and "IP=
source guard". The features can vary, depending on your model of swit=
ch.<br>
<br>Here is one example of Cisco's documentation. This one is for 3550 =
switches. <a href=3D"http://www.cisco.com/en/US/docs/switches/lan/catalyst3=
550/software/release/12.2_25_see/configuration/guide/swdhcp82.html" target=
=3D"_blank">http://www.cisco.com/en/US/docs/switches/lan/catalyst3550/softw=
are/release/12.2_25_see/configuration/guide/swdhcp82.html</a><br>
<br><br>Bruce Osborne<br>Network Engineer<br>IT Network Services<br><br><a =
href=3D"tel:%28434%29%20592-4229" target=3D"_blank">(434) 592-4229</a><br><=
br>LIBERTY UNIVERSITY<br>Training Champions for Christ since 1971<br><br>Fr=
om: Hall, Rand [mailto:<a href=3D"mailto:hallr@MERRIMACK.EDU" target=3D"_bl=
ank">hallr@MERRIMACK.EDU</a>]<mailto:[mailto:<a href=3D"mailto:hallr@MER=
RIMACK.EDU" target=3D"_blank">hallr@MERRIMACK.EDU</a>]><br>
Sent: Monday, April 30, 2012 12:39 PM<br>Subject: Re: SOHO WiFi routers and=
residential networking<br><br>Sheila,<br><br>Good luck blocking rogues. :-=
) Your best bet is to hold to your commitment to providing service to the j=
ack. To that you can add some basic best practice suggestions to people who=
want to try using a wireless router or bridge (enable encryption, negotiat=
e channel selection with neighbors, etc).<br>
<br>Your network folks will want to turn on DHCP Snooping. Sometimes a resi=
dent will plug a router in "backwards" and offer up DHCP leases t=
o their neighbors--not a pretty sight. If they are new to Cisco they might =
appreciate a sample interface config for some ideas. Feel free to share:<br=
>
<br>=A0switchport access vlan xx<br>=A0switchport mode access<br>=A0switchp=
ort protected<br>=A0switchport port-security maximum 6<br>=A0switchport por=
t-security<br>=A0switchport port-security aging time 1<br>=A0switchport por=
t-security violation restrict =A0switchport port-security aging type inacti=
vity =A0ip arp inspection limit rate 15 burst interval 10 =A0storm-control =
broadcast level pps 50 10 =A0storm-control multicast level pps 50 10 =A0spa=
nning-tree portfast =A0spanning-tree bpduguard enable =A0ip verify source =
=A0ip dhcp snooping limit rate 10<br>
<br><br>Rand<br><br>Rand P. Hall<br>Director, Network Services =A0 =A0 =A0 =
=A0 =A0 =A0 =A0 =A0 askIT!<br>Merrimack College<br><a href=3D"tel:978-837-3=
532" target=3D"_blank">978-837-3532</a><tel:<a href=3D"tel:978-837-3532"=
target=3D"_blank">978-837-3532</a>><br>
<a href=3D"mailto:rand.hall@merrimack.edu" target=3D"_blank">rand.hall@merr=
imack.edu</a><mailto:<a href=3D"mailto:rand.hall@merrimack.edu" target=
=3D"_blank">rand.hall@merrimack.edu</a>><br><br>If I had an hour to save=
the world, I would spend 59 minutes defining the problem and one minute fi=
nding solutions. - Einstein<br>
<br>On Fri, Apr 27, 2012 at 1:48 PM, Crowe, Sheila <<a href=3D"mailto:sh=
eila@montana.edu" target=3D"_blank">sheila@montana.edu</a><mailto:<a hre=
f=3D"mailto:sheila@montana.edu" target=3D"_blank">sheila@montana.edu</a>>=
;> wrote:<br>
In early March, I participated in a thread started by Jeannie Abney about w=
hat other schools' polices are for residents bringing personal wireless=
routers onto your network. =A0I added some questions pertaining to single =
family apartments (vs. residence halls) and got some great feedback. =A0I w=
ould like to take it a step further and ask some more questions based on th=
e type of network that we have.<br>
<br>We have a Cisco network, a core at the origin of the commodity internet=
pipe, and a subnet for each of our buildings (really areas). =A0In the res=
idence halls we have a large Aruba wireless network installed so that every=
building is blanketed for secure wireless internet access. =A0 In the resi=
dence halls, ResNet is charged out to every resident regardless of whether =
they use it or not.<br>
<br>We do not provide ubiquitous wireless coverage in family housing becaus=
e ResNet is an opt-in service. Additionally, our family housing area was wi=
red about 13 years ago and only provided one wired jack per apartment. As I=
'm sure you can imagine, virtually every customer in family housing has=
a soho wireless router. =A0When we upgraded this section of our network (f=
rom 3Com switches to Cisco), we immediately had a BIG problem with our netw=
ork dropping constantly. =A0It was ultimately decided that it was the SOHO =
wireless routers causing the problem; namely, unicast packet floods through=
our Cisco switch ports. Only recently it was discovered that Cisco switche=
s have a feature that will block unicast and multicast floods. =A0We are de=
ploying this slowly.<br>
<br>Now for the questions. For those of you who have a similar network, do =
you employ this Cisco feature or do you simply block all "rogue" =
wireless connections? =A0Or do you have another measure in place to deal wi=
th the unicast packet floods? =A0Also, do your network engineers consider t=
his a stopgap measure ("band-aid") to deal with residences where =
you do not offer WiFi?<br>
<br>Please do share all of the details about this issue (or non-issue) on y=
our network as you know them. =A0And thanks a million!<br><br>Sheila Crowe<=
br>Montana State University ResNet<br><a href=3D"tel:406.994.4230" target=
=3D"_blank">406.994.4230</a><tel:<a href=3D"tel:406.994.4230" target=3D"=
_blank">406.994.4230</a>><br>
<a href=3D"tel:406.209.7243" target=3D"_blank">406.209.7243</a><tel:<a h=
ref=3D"tel:406.209.7243" target=3D"_blank">406.209.7243</a>><br><br>P.S.=
I'm hoping to see all of you at the 2012 Student Technology Conference=
at Claremont Colleges!<br>
<br>___________________________________________________ You are subscribed =
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e archives, go to <a href=3D"http://LISTSERV.ND.EDU/archives/resnet-l.html"=
target=3D"_blank">http://LISTSERV.ND.EDU/archives/resnet-l.html</a> ______=
_____________________________________________<br>
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_____________________________________________<br>
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get=3D"_blank">http://LISTSERV.ND.EDU/archives/resnet-l.html</a> __________=
_________________________________________<br>
___________________________________________________ You are subscribed to t=
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_________________________________________<br>
<br>This email and any attachments may contain confidential and proprietary=
information of Blackboard that is for the sole use of the intended recipie=
nt. If you are not the intended recipient, disclosure, copying, re-distribu=
tion or other use of any of this information is strictly prohibited. Please=
immediately notify the sender and delete this transmission if you received=
this email in error.<br>
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get=3D"_blank">http://LISTSERV.ND.EDU/archives/resnet-l.html</a> __________=
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ed to the ResNet-L mailing list.<br><br>To subscribe, unsubscribe or search=
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___________________________________________________<br><br>________________=
___________________________________<br>You are subscribed to the ResNet-L m=
ailing list.<br><br>To subscribe, unsubscribe or search the archives,<br>
go to <a href=3D"http://LISTSERV.ND.EDU/archives/resnet-l.html" target=3D"_=
blank">http://LISTSERV.ND.EDU/archives/resnet-l.html</a><br>_______________=
____________________________________<u></u><u></u></p></div></div></div><p =
class=3D"MsoNormal">
<br><br clear=3D"all"><u></u><u></u></p><div><p class=3D"MsoNormal"><u></u>=
=A0<u></u></p></div><p class=3D"MsoNormal">-- <br>Chris Webster<br>Senior T=
echnician<br>OIT Walk-in Center<br>North Carolina State University<br><br>P=
h: <a href=3D"tel:919.513.2676" value=3D"+19195132676" target=3D"_blank">91=
9.513.2676</a><br>
Fax: <a href=3D"tel:919.513.2945" value=3D"+19195132945" target=3D"_blank">=
919.513.2945</a><br>Email: <a href=3D"mailto:chris.webster@ncsu.edu" target=
=3D"_blank">chris.webster@ncsu.edu</a><br>Web: <a href=3D"http://go.ncsu.ed=
u/wic/" target=3D"_blank">http://go.ncsu.edu/wic/</a><u></u><u></u></p>
</div><p class=3D"MsoNormal">______________________________________________=
_____ You are subscribed to the ResNet-L mailing list. <u></u><u></u></p><p=
>To subscribe, unsubscribe or search the archives, go to <a href=3D"http://=
LISTSERV.ND.EDU/archives/resnet-l.html" target=3D"_blank">http://LISTSERV.N=
D.EDU/archives/resnet-l.html</a> __________________________________________=
_________ <u></u><u></u></p>
<p class=3D"MsoNormal"><br><span style=3D"font-size:10.0pt;font-family:&quo=
t;Arial","sans-serif";color:blue">This email and any attachm=
ents may contain confidential and proprietary information of Blackboard tha=
t is for the sole use of the intended recipient. If you are not the intende=
d recipient, disclosure, copying, re-distribution or other use of any of th=
is information is strictly prohibited. Please immediately notify the sender=
and delete this transmission if you received this email in error.</span><u=
></u><u></u></p>
<p class=3D"MsoNormal">___________________________________________________ =
You are subscribed to the ResNet-L mailing list. <u></u><u></u></p><p>To su=
bscribe, unsubscribe or search the archives, go to <a href=3D"http://LISTSE=
RV.ND.EDU/archives/resnet-l.html" target=3D"_blank">http://LISTSERV.ND.EDU/=
archives/resnet-l.html</a> ________________________________________________=
___ <u></u><u></u></p>
</div></div></div></div><div class=3D"HOEnZb"><div class=3D"h5">___________=
________________________________________
You are subscribed to the ResNet-L mailing list.
<p>
To subscribe, unsubscribe or search the archives,
go to <a href=3D"http://LISTSERV.ND.EDU/archives/resnet-l.html" target=3D"_=
blank">http://LISTSERV.ND.EDU/archives/resnet-l.html</a>
___________________________________________________
</p></div></div></blockquote></div><br><br clear=3D"all"><div><br></div>-- =
<br>Chris Webster<br>Senior Technician<br>OIT Walk-in Center<br>North Carol=
ina State University<br><br>Ph: 919.513.2676<br>Fax: 919.513.2945<br>Email:=
<a href=3D"mailto:chris.webster@ncsu.edu" target=3D"_blank">chris.webster@=
ncsu.edu</a><br>
Web: <a href=3D"http://go.ncsu.edu/wic/" target=3D"_blank">http://go.ncsu.e=
du/wic/</a><br>
</div></div>
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--e89a8ff255aeae933b04bf26d480--
