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

joel jaeggli joelja at
Tue Jun 10 18:10:53 UTC 2014

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 at> 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:
>> 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

your rib should be the sum of all received routes that you did not filter.

> and the FIB
> contains only the "best path" entries from the RIB, wouldn't the FIB be
> at or below 300k?

a live example of rib size from a router with two transit providers.

bird> show route count
979842 of 979842 routes for 490932 networks

a live example of rib size from a router with one ibgp peer with addpath
and three  upstream transit providers

bird> show route count
1471242 of 1471242 routes for 491977 networks

> --Blake

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