WAN + LAN routing

sam_manay · ‎06-08-2010

Dear All,

What is the best practice of the routing for LAN and WAN,

Is it OSPF & BGP or EIGRP & BGP?

Really appreciated for any reply.

Regards,

sam

Jon Marshall · ‎06-08-2010

Sam

There is no best practice as such. OSPF/EIGRP can be used both as LAN routing protocols and WAN routing protocols and they both work well. It really depends on the size of your network and whether or not you have multiple exit and entry points into your sites from the WAN.

In addition you may find that if you run MPLS with a Service Provider they will dictate which routing protocol(s) you can use to peer with them. So lat place i worked we had an ATM network and used EIGRP as out LAN and WAN routing protocol. This worked fine but it did rely on being able to summarise effectively from each site into the WAN.

We then upgraded to MPLS and the provider only used BGP to peer with them so we had EIGRP as our LAN protocol and BGP as our WAN protocol.

BGP comes into it's own when you have multiple exit/entry points into your sites and you want to influence the paths traffic will take ie. some over one path, some over the other.

Jon

sam_manay · ‎06-08-2010

Hi Jon,

FYI, the client'd to use BGP (MPLS/VPN),

I read from a forum, some like to use OSPF-BGP due to the both can work easily insted of

having EIGRP-BGP.

I understand that once our the Cisco, it is fair to use EIGRP routing.

You are pointing to the size of network as a concern,

Which one will be use once the for bigger network (EIGRP or OSPF)?

Many thanks for kind reply.

Rgds,

sam

Jon Marshall · ‎06-08-2010

sam_manay wrote:

Hi Jon,

FYI, the client'd to use BGP (MPLS/VPN),

I read from a forum, some like to use OSPF-BGP due to the both can work easily insted of

having EIGRP-BGP.

I understand that once our the Cisco, it is fair to use EIGRP routing.

You are pointing to the size of network as a concern,

Which one will be use once the for bigger network (EIGRP or OSPF)?

Many thanks for kind reply.

Rgds,

sam

Sam

The size of the network is only really a concern if you are running the same routing protocol for both LAN and WAN. If you are running BGP for the WAN then you can use either OSPF or EIGRP for the LANs because each OSPF/EIGRP LAN is not connected to the other LANs except via BGP.

If you were only running one routing protocol across your LAN and WAN then OSPF lends itself more to large networks because it is hierarchical in design with the use of areas whereas EIGRP is flat.

Whether to use EIGRP or OSPF with BGP is really a matter of which you are happier with. EIGRP works perfectly well with BGP as does OSPF.

Jon