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New Member

OSPF and EIGRP neighborship....

Hi,

I've configured a simple hub and spoke Frame Relay networks with standard physical interface (not sub-interfaces) and with Frame Relay Inverse arp enabled and I'v tried to configure a routing protocol, ospf first and eigrp last.

I've noted that because the medium is a NBMA, with opsf I've had to specify the "ip ospf network broadcast" at the interfaces level to see a neighborship success, correct!

With eigrp the neighborship work well even if I've specified nothing to declare the network broadcast...

The hello packet are multicast for the first and for the second! can anyome explane me this ? ? ?

thank's in advance!

Graziano

My question is:

7 REPLIES
New Member

Re: OSPF and EIGRP neighborship....

OSPF does not recognize frame relay as a broadcast network (hence the NBMA). OSPF won't try to initiate a neighbor relationship on this type of network, you must specify the neighbors manually. In your case, you've change the default OSPF network type to Broadcast... OSPF will look for neighbors in this case.

Since you're using inverse-arp, broadcasts and multicasts are forwarded over the frame cloud.

Mick.

New Member

Re: OSPF and EIGRP neighborship....

Thank's very much, but...

why eigrp work well???

Graziano

Gold

Re: OSPF and EIGRP neighborship....

Because EIGRP doesn't attempt to create a DR/BDR on the non-broadcast segment.

Russ

New Member

Re: OSPF and EIGRP neighborship....

Hi.

OSPF will only work properly in a scenario like yours (broadcast on Frame-Relay interface) if you have a Frame-Relay full-mesh among all the routers. OSPF may work fine without the full mesh, but the packet forwarding itself may not work without the full mesh because the next-hop for a certain route can be a spoke and the router only has frame-relay dynamic mappings for routers to which it has PVCs. If you have a Hub & Spoke topology, each spoke will only have a PVC to the Hub router and not to each spoke.

Rgds.

NM

New Member

Re: OSPF and EIGRP neighborship....

Thank's,

but That I don't understand is:

why ospf and eigrp send multicast hello packet on the same media but the first doesn't work because this media is nbma instead the last work well???

Graziano

New Member

Re: OSPF and EIGRP neighborship....

Correct, but must create a neighborship with multicast hello packet, it isn't quite the same?

Graziano

Gold

Re: OSPF and EIGRP neighborship....

No, it's not.... All the routers have to agree on who the dr and bdr are with OSPF. Since they can't all see each other's hello's, they won't agree, and thus it won't work. With eigrp, all you care about is actually receiving the multicast hello packets.

Russ

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