How many BGP routes can C3825 store

[gbcbooksmj]

Hi all

please check my device screenshot

i used to store more then 120,000 routes on my C3825 router

but from the log output  , my device was out of memory to store BGP route , and the total numbers of BGP routes was only more 52,000.

any one know what is going on ?

[Julio E. Moisa]

Hi

It is a lot routes, are you connected this router to Internet using BGP? It could be being used as a transit router and that is a problem.

If it is a transit router you could block  this traffic and avoid be a transit router using ASpath acl + Regular expressions.

[gbcbooksmj]

no i did not connect it as a transit router . 

[Georg Pauwen]

Hello,

do you actually need all those 52000 routes ? You obviously could consider route filtering, or working with just default routes.

Either way, check your config for stuff like 'soft reconfiguration inbound/outbound' which as far as I remember doubles the size of the routing table, but is not needed anymore in the latest BGP release.

[gbcbooksmj]

yes , i need them all , actually  , there will be more .

[Georg Pauwen]

Hello,

the total memory usage for BGP depends on more factors than only the amount of routes. Can you post the full configuration of your router ?

[gbcbooksmj]

ok

the memory of my c3825 , it show the totoal 's 78MB , do you know what it going on ? 

[Georg Pauwen]

Hello,

can you post the output of:

show platform

That output should give you the exact amount of memory...

[Georg Pauwen]

Hello, 

52000 routes shouldn't be a problem, if you consider that for the full BGP table (>500K routes) you need about 1 Gigabit of memory.

That said, can you post the configuration of the router, as well as the output of 'show version' ?

[gbcbooksmj]

here is the soft version of my c3825 .

as the previous attchment , you can see the total memory of c3825 is 77878592Byte = 74MB , it should be 220MB from the version showing.

@Julio Moisa

no i did not connect it as a transit router . 

[paul driver]

Hello

sh ip bgp neighbors | in Prefix
sh ip bgp sum

Following on from Julo mentioned you can become a transit AS if you peer with two different ISP's and unwittingly adverted their routes to each other, to negate that.a simple regex command would be required.

Regards soft-reconfiguration, Georg is correct this is very resource intensive and nowadays int required - Please review this

Below are the commends to prohibit becoming a transit AS and having soft-reconfiguration inbound disabled>

Example:
ip as-path access-list 10 permit ^$ ( local routes only)

router bgp xx
neighbor <isp1>  filter-list 10 out
no neighbor <isp1> soft-reconfiguration inbound
neighbor <isp2> filter-list 10 out
no neighbor <isp2> soft-reconfiguration inbound


res
Paul

[gbcbooksmj]

i did not enable soft-configuration . 

do you think any incorrect any on the memory info  ?

[jonathan.cuthbert]

I had always understood that a Full BGP table in modern times (2017) was more around the lines of 8 GB of memory.  I have found this to be true with the ISR4k.

[gbcbooksmj]

any reply  ?