EIGRP question

Unanswered Question
Feb 27th, 2010
User Badges:

I have a remote site (network 10.80.180.0) which is accessing two data centers through MPLS. Two data centers are running the same EIGRP on their network and both update carrier BGP with eigrp routes. Both data centers are connected with L2 (dark fiber) and with L3 MPLS. In data center AAA network is 10.80.100.0 and in data center BBB 10.80.150.0. Routers from both datacenters update carrier BGP with the same routes. It is causing some routing issues.

For example:

When PC from remote site on network 10.80.180.0 wants to access Mail Server (10.80.100.100) in data center AAA it goes directly to data center AAA. Then mail server replys to this PC by sending packets to default gateway 10.80.100.1. This router however learns route to 10.80.180.0 from router in datacenter BBB so it sends packets to router in datacenter BBB and he sends packets to 10.80.180.0 network. It creates asymetric routing. Packet leave network 10.80.180.0 and goes to network 10.80.100.0 and returns back from network 10.80.150.0.

Carriers wants me to tag eigrp routes leaving network 10.80.100.0 with different tag than routes leaving 10.80.150.0 network.

Should I do it?  If yes, how this can be done?


I think it is complicated explanation. If required I can provide diagram.


Any help appreciated

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Loading.
Giuseppe Larosa Mon, 03/01/2010 - 04:27
User Badges:
  • Super Silver, 17500 points or more
  • Hall of Fame,

    Founding Member

Hello Zbigniew,

how is the the remote site with IP subnet 10.80.180.0 connected to the MPLS network?

Is it a VRF site in an MPLS L3 VPN service?

if so, what routing protocol is used between the remote site CE and the PE node?


>> by sending packets to default gateway 10.80.100.1. This router however  learns route to 10.80.180.0 from router in datacenter BBB so it sends  packets to router in datacenter BBB


is this happening via the L2 path between the two data centers or via the service provider network?


>> Routers from both datacenters update carrier BGP with the same routes


this would lead to eBGP as PE-CE routing protocol with EIGRP redistributed into BGP.


>>

Carriers wants me to tag eigrp routes leaving network 10.80.100.0  with different tag than routes leaving 10.80.150.0 network.

Should  I do it?  If yes, how this can be done?


This is wise and highly recommended because it is likely that you have built two points of mutual redistribution (bidirectional) between BGP and EIGRP.

This would explain the unwanted path taken by return traffic to remote site.


to do this you need to use route-maps and to set a route-tag


example:


site AAA

route-map EIGRPtoBGP permit 10

match ip address 11

set tag 1010


router bgp yourASN

red eigrp XX route-map EIGRPtoBGP



site BBB:


route-map EIGRPtoBGP2 permit 10

match ip address 11

set tag 2020


router bgp yourASN

red eigrp XX route-map EIGRPtoBGP2


this is just an example, your scenario may require further tuning, specially to avoid to advertise unwanted prefixes.


for this reason the use of an access-list or a prefix-list can be helpful to specify what EIGRP prefixes should be redistributed into BGP.


to be noted that you could avoid mutual redistribution by using network commands in router BGP process.

Network command allows in BGP to advertise a prefix if present in the IP routing table not only for connected routes.


I would suggest you to attach a network diagram, configurations of CE routers of DC AAA and DC BBB and of remote site CE router.


Hope to help

Giuseppe

Actions

This Discussion