Why this BGP configuration didn't advertised routes?

[m-abooali]

hi,

I was trying to turn up our BGP session with a new provider as part of our transition to a whole nw infrastructure but after BGP session was Established, I reliased that no Prefixes have been advertised to our Peer or upstream provider!

here is my configuration, pls see if you can find any problems and advise acordingly:

router bgp xxxx

no synchronization

bgp log-neighbor-changes

network 198.x.144.0

network 216.x.192.0 mask 255.255.240.0

network 216.x.224.0 mask 255.255.224.0

network 216.x.224.0 mask 255.255.240.0

neighbor 216.x.125.241 remote-as xxxx

neighbor 216.x.125.241 prefix-list default in

neighbor 216.x.125.241 prefix-list secondblock out

no auto-summary

!

ip classless

!

no ip http server

!

!

ip prefix-list default seq 5 permit 0.0.0.0/0

!

ip prefix-list secondblock seq 10 permit 216.x.192.0/20

ip prefix-list secondblock seq 15 permit 216.x.224.0/19

I use EIGRP for iGP and when we stoped our current BGP session with the old provider to start using the new provider, I startwed seeingall those 216.x.x.x blocks (above in the network statemnet) coming to this border router as /24s.

that being said, BGP should know that it should advertise them in /20 and /19 but

i couldn't see any route or prefixes being advertised to our new provider, we though received the default routes from them but nothing out to them!!?

i tried to clear bgp soft in a soft out but made no difference.

Should the "NULL0" statemnet be also in the router configuration for BGP advertisement to work?

please advise.

Regards,

Mike

[cisco_lad2004]

U need to have a route for the prefix u want to advertise, else BGP will not advertise it.

so you are correct in mentioning a null 0 static route as it would create a static route.

You are seeing /24 which you then summarize to your peering partner via network statement.

HTH

Sam

[m-abooali]

Sam,

can you please show me how?

I really apprecitae that as my time is very short for doing this.

Regards,

Masood

[cisco_lad2004]

conf t

ip route 216.x.224.0 255.255.240.0 null 0

then verify this by doing sh ip bgp neighbor x.x.x.x advertise-routes and hopefully it wil be there.

HTH

Sam

[m-abooali]

Sam do I need one of these ip routes for each block thatwe have?

Do I need one for the BGP neighbore Ip address too ?

Thx,

Mike

[cisco_lad2004]

yes u need it to match each network statement u have under BGP process.

no neighbor ip address is needed, just:

ip route subnet mask null0 (for the 3 prefixes).

I suggest you do one at the time to validate.

Sam

[m-abooali]

Thanks Sam, I will let you know the result if its OK with you. here is what I am going to add to my BGP cocnfiguration and I do the ame fo rour second provider in my yfirst router facing the second provider.

ip classless

ip route 216.x.192.0 255.255.240.0 null 0

ip route 216.x.224.0 255.255.240.0 null 0

ip route 216.x.224.0 255.255.224.0 null 0

Please advise.

Mike

[lamav]

Sam:

While using a static route pointing to null0 will work, isn't it a better approach to use a recursive static route in the event that the edge router loses connectivity to internal networks?

Just thinking out loud...

Thanks

Victor

[cisco_lad2004]

Victor,

Nulled static route is just a "bate", once packets hits the peering router, you have to rely on longest from IGP for example.

And IGP would typically have redundant path.

the aim here, is to simply create an entry so BGP can advertise the summarized prefix. more specific entries will still be present.

I hope thsi clarifies it.

Sam

[m-abooali]

so,

these new ip route to Null0 must do the trick in my case?

here they are:

ip classless

ip route 216.x.192.0 255.255.240.0 null 0

ip route 216.x.224.0 255.255.240.0 null 0

ip route 216.x.224.0 255.255.224.0 null 0

Please advise.

Mike

[cisco_lad2004]

yes !

[m-abooali]

Thanks very much. I will return to let you kno wthe result and also, rate the posting.

Regrads,

Mike

[Harold Ritter]

Masood,

I don't mean to rub it in but if you look at the response to your posting earlier last week, I had mention that you should have these routes in your routing table:

"Also, make sure you have routes, matching the network statements, that are installed in the RIB. "

http://forums.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Network%20Infrastructure&topic=LAN%2C%20Switching%20and%20Routing&topicID=.ee71a04&CommCmd=MB%3Fcmd%3Dpass_through%26location%3Doutline%40%5E1%40%40.2cc06535/0#selected_message

Regards,

[m-abooali]

i don't see it like that at all. I must have flollowed the same posting but under pessure and datacenter down, people bagging, i kind of lost it altogether.

i fixed the netwoke statement when we spoke last but what happend is this:

Someone tripped over a wire and pulled my laptop, dropped it down form a 5 feet hight bench and machine broke. I lost all my data and configurations, then, two SUPS 720 went bad on these 6506s (they were purchased refurbished!) and I had to change the SUPS an dput new ocnfiguration on the routers, between all these incidents, the network statement and my IP routes to Null0 got lost!.

Last night, I had only 15 minutes to bring these circuits up and troublshoot as necessary given that I had to spend 5 hours troublshooting two crosse-connects just because they didn't want to invest andn buy SFps to use fiber. The media convertors form Fiber (single mode) to copper rj45 wasn't working and I had to fix those too.

so, I lost it altogether whe it came to trobleshooting the BGP. it was Established but no prefixes were geting advertised.

I still need to put these ip routes (Null0) staements and see if the problems go away.

I am sorry for not following the same posting.

(since, Masood was kind of difficult for many to pronounce, I have choosen Mike for my coworkers to call me, so, I am the same person!)

Regards,

Mike

[lamav]

Sam:

Thanks for the feedback.

I understand that the purpose of the null0 route is to place a route in the IP routing table so that BGP can advertise it. That BGP requirement has to be met...

What Im saying is that if the edge router loses connectivity to the internal network, there is no mechanism in place to keep BGP from advertising the unreachable networks and creating a blackhole. IOW, you want BGP to stop advertising the route if that network becomes unreachable. With a null0 route, the route will always be in the routing table...unconditionally.

Dont ge me wrong, Im not really advocating one method or the other. I was sort of thinking out loud and wanted your feedback, but I also wanted you to know exactly what my rationale is...

[EDIT] Im sorry, let me illustrate what Im saying. I refer to another metod, but never show it.

If the internal network is 135.10.1.0/24, a recursive static route to the effect of ip route 135.10.0.0 255.255.0.0 135.10.1.1 can be used to ensure that the route is both in the routing table, BUT also with the caveat that the edge router has connectivity to the internal network if its going to advertise it.[EDIT]

Thanks

Victor