[172285] in North American Network Operators' Group
Re: Getting pretty close to default IPv4 route maximum for 6500/7600
daemon@ATHENA.MIT.EDU (Matthew Petach)
Tue Jun 10 20:03:18 2014
X-Original-To: nanog@nanog.org
In-Reply-To: <53975019.1040206@ispn.net>
Date: Tue, 10 Jun 2014 17:03:09 -0700
From: Matthew Petach <mpetach@netflight.com>
To: Blake Hudson <blake@ispn.net>
Cc: "nanog@nanog.org" <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
On Tue, Jun 10, 2014 at 11:36 AM, Blake Hudson <blake@ispn.net> wrote:
>
> joel jaeggli wrote the following on 6/10/2014 1:10 PM:
>
> On 6/10/14, 10:39 AM, Blake Hudson wrote:
>>
>>> =C5=81ukasz Bromirski wrote the following on 6/10/2014 12:15 PM:
>>>
>>>> Hi Blake,
>>>>
>>>> On 10 Jun 2014, at 19:04, Blake Hudson <blake@ispn.net> wrote:
>>>>
>>>> In this case, does the 512k limit of the 6500/7600 refer to the RIB
>>>>> or the FIB? And does it even matter since the BGP prefix table can
>>>>> automatically be reduced to ~300k routes?
>>>>>
>>>> Te 512k limit refers to FIB in the B/C (base) versions of 6500/7600
>>>> Supervisors and DFCs (for line cards). BXL/CXL versions have FIB for
>>>> 1M IPv4 prefixes.
>>>>
>>>> You can find more information here:
>>>>
>>>> http://www.cisco.com/c/en/us/support/docs/switches/
>>>> catalyst-6500-series-switches/117712-problemsolution-cat6500-00.html
>>>>
>>>>
>>>> And yes, you=E2=80=99re right - no matter how many neighbors you have,=
the FIB
>>>> will only contain best paths, so it will be closer to 500k entries in
>>>> total rather than N times number of neighbours.
>>>>
>>>> Please correct me if I'm wrong, but if the BGP table contains ~500k
>>> prefixes, which are then summarized into ~300k routes (RIB),
>>>
>> Unlikely, just because prefixes could be cidr aggregated doesn't mean
>> they are. the more specifics exist for a reason, in the case of
>> deaggrates with no covering anouncement, well not much you're doing with
>> those.
>>
>> your rib should be the sum of all received routes that you did not filte=
r.
>>
> On the couple Cisco platforms I have available with full tables, Cisco
> summarizes BGP by default. Since this thread is talking about Cisco gear,=
I
> think it's more topical than results from BIRD.
>
> One example from a non-transit AS:
> ASR#sh ip route sum
> IP routing table name is default (0x0)
>
> IP routing table maximum-paths is 32
> Route Source Networks Subnets Replicates Overhead Memory
> (bytes)
> connected 0 10 0 600 1800
> static 1 2 0 180 540
> application 0 0 0 0 0
> bgp xxxxx 164817 330796 0 29736780 89210340
> External: 495613 Internal: 0 Local: 0
> internal 5799 20123680
> Total 170617 330808 0 29737560 109336360
>
>
I'm not sure you're reading that correctly.
164817+330796 =3D 495613
That is, the BGP routing table size is the
union of the "Networks" and the "Subnets";
it's not magically doing any summarization
for you.
Matt
