Re: Getting pretty close to default IPv4 route maximum for 6500/7600 routers.

[Matthew Petach <mpetach () netflight com>]

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:
> > > Łukasz 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’re 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 filter.
> 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 = 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