Advertised-routes received-routes from ISP

[mahesh18]

We have EBGP neighbour with ISP.

When I run below command

show ip bgp neighbors 72.29.x.xpaths advertised-routes received-routes

% Inbound soft reconfiguration not enabled on 72.29x.x

it does not show any routes learned from the nei?

does it mean that we are not learning any routes from this nei?

[paul driver]

Hello

bgp will probably have route refresh capability so you can try

sh ip bgp neighbor xxxx routes

sh ip bgp neighbor xxxx received-routes

[mahesh18]

when i run sh ip bgp neighbor xxxx routes

i see a ll the routes from nei like

Network Next Hop Metric LocPrf Weight Path
* 1.0.64.0/18 72.29.x.x                  0 25983 6327 2497 7
* 1.0.128.0/24 72.29.x.x                0 25983 6327 4766 3

when i run sh ip bgp neighbor xxxx received-routes

i get same error message so what is difference between the two commands please ?

[Giuseppe Larosa · Accepted solution]

Hello Mahesh,

as explained by Seth your configuration is missing an optional command for soft-reconfiguration inbound:

% Inbound soft reconfiguration not enabled on 72.29x.x

When you use the show command that end with received-routes the router would like to show you the receveid routes before any inbound policy is applied.

The router can do this only by storing all the received routes from neighbor in a separate table.

So if you enable soft reconfiguration inbound you will double the memory used on the router to store the routes from this neighbor one copy as they are received one copy after inbound policy is applied.

If this is the neighbor from which you receive the full BGP table you are dealing with more then 740,000 routes you should think of it carefully.

the show ... routes shows the routes after the inbound policy is applied.

Hope to help

Giuseppe

[paul driver · Accepted solution]

Hello

so just like to add to what the other guys have stated -

Route -refresh dosent require the bgp router to allocate a separate unedited table of bgp routes from it bgp neighbours  when it wants to run a query for updates- which is exactly what needs to be done if RR isn't supported by the bgp rtrs  -As then they would need use this soft -inbound configuration which as you now can gather would be much more resource intensive to the rtrs if thry had a full internet routing table to query.

[Seth Beauchamp]

you may need to add "neighbor 1.1.1.1 soft-reconfiguration inbound". This command will keep a second pre-policy (before modifications by prefix lists, route-maps etc) copy of the routes received from the neighbors, so if there are lots of routes you may need to consider memory implications on your router. I believe you may need to bounce the peer after adding this as well.