advanced BGP - need expertise

[rajivrajan1]

Hi,

For ease understanding , I explained the network simply.

1. CE has BGP connection to PE

2.CE router has a backdoor connection (IGP -EIGRP) - the updated of eigrp are adverised back to PE again.

in simple words , same prefix is received from PE and advertised also to PE.

So solve the issue,

while redistributing form EIGRP to BGP , I have changed the wight and Local prefrecne to 0. So bgp always prefers the external ( towards PE ) path. ( that is the requirement)

Everything works as expected, MPLS is primary ,  backdoor is secondary.. no issues.

now question:

when i redistribute and the MLPS link is UP , I am expecting two prefixes to be shown in bgp table , but its not showing ,, it shows only external PE recived routes., but when the primary fails,  backdoor links kicks in and bgp starts to show that,.....

any clues ,... ?

[Giuseppe Larosa · Accepted solution]

Hello Rajivrajan1,

only routes that are installed in the IP routing table are passed from one protocol to the other in your case from EIGRP to BGP.

This is how redistribution works.

so what you see is normal.

only I recommend to test both failure and restore of eBGP session to see if when the BGP session comes back the eBGP route is preferred.

As soon as the eBGP route is installed, the EIGRP route is not injected in the BGP table

Hope to help

Giuseppe

[rajivrajan1]

Jeeez i knew this.. haaa...how did it not clicked to me......anyway... awesome response... thanks a lot..rated u full..

[rajivrajan1]

hi ,

i did a redistribute eigrp to bgp with a route map setting weight and local preference to 0 ...

Things worked fine in a 2600 ( dynamips) but in real network ( 2800) bgp said "not advertised to any peer"

I could see the route in eigrp , it was getting redistributed to bgp and get and bgp table entry was there with not advertised to any peer .... I was clue less .. any ideas?

[Dan-Ciprian Cicioiu]

Hi ,

are you sure that the prefix is in the routing table via EIGRP ( AD 90/170 ) and not  via eBGP ( AD 20 ) ?

Dan

[rajivrajan1]

yes I am , because for that prefix to enter , there is no other way .. I had the EIGRP

route prensent in routing table and redistributing " advertising via bgp "

and then in bgp table this was the case...

sh ip bgp 10.70.8.0
BGP routing table entry for 10.70.8.0/29, version 460583
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Flag: 0x820
  Not advertised to any peer
  Local
    10.66.246.253 from 0.0.0.0 (128.212.44.210)
      Origin incomplete, metric 52802816, localpref 0, valid, sourced, best

[Dan-Ciprian Cicioiu]

Please post

show ip route 10.70.8.0

[rajivrajan1]

sorry do not have that one now ... Activity failed.. ha

But I am sure it was showing  EIGRP route...

[Dan-Ciprian Cicioiu]

I dont undestand , the route is via EIGRP or BGP ?

paste :

show ip route 10.70.8.0 255.255.255.248

[rajivrajan1]

ok here you go ... ( i am not giving the entire network picture and background since it would be boring to read 3 ,4 pharagraphs .. also type )

Router A - B are connected with ethernet and running EIGRP. EIGRP is getting redistributed into BGP in router B .. Route B need to advertise this BGP path to MPLS CLOUD....  For some reasons( Reasons are given in above posts ) , While redistributing I am reducing the Weight and Local preference to 0 ... The path reaches BGP table... and says " not advertisied to any peer "

Thats waht you are seeing in the bove output....

Same thing i emulated and its working fine with 2691 .. advance enterprise...

real network 2800 nm advanceenterprise.. i still didnt get a clue why it did not advertise out.. this was the best path .. and only availabel path tooo.....

[Dan-Ciprian Cicioiu]

Then check the out filters on that neighbor , you should also allow the prefix.

[rajivrajan1]

I am sorry to say all negative answers .. though thats not my objective ...

It dont have any filters... Same routes are getting advertised , if I did not set down the Loca

l preference and weight to 0  while redistribution....

It just downt advertise out if I set thiese thing down to 0 in production ... but with the same setup , and setting these prefixes down .. 2691 could advertise the prefix in my lab .. thats what is being real head scratcher...