Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements
Webcast-Catalyst9k
New Member

OSPF

i am confused abt one thing and would be veru oblidged if someone help me out.....i reacintly configured a ospf on one of my lab routers (name A)and then configured a loopback address as well (just wanted to check) then i advertised my serial link ip address with network command 211.x.x.1 0.0.0.0 area 0 as well as on the ethernet

i configured the same thing on the other router (directly connected, name b) now the the router b was geting router a ethernet network but router a was not getting anything.....when i issued the command show ip protocol......the loop address was coming on undergateway....first of all why is that??? secondly when i issued show route command on router A......i saw something v strange (or may be i dont know that) under directly connected network there was another network which was the same ip of the serial but coming with /32 mask.....i was like...never seen that thing before.....thanks in advance

6 REPLIES
Hall of Fame Super Bronze

Re: OSPF

Please post configs.

Silver

Re: OSPF

Please refer to below link if you are using PPP encapulation. Otherwise, please provide config.

http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a0080094057.shtml

Hope this helps.

New Member

Re: OSPF

About router A not getting anything from Router B, if router B does not have any active interfaces other than the serial intf included in the OSPF process, then router B will not have any route to send to A.

show ip protocols command will display the Router ID of the OSPF router. OSPF uses the IP address of the loopback interface as the Router ID (if multiple loopback interfaces are configured, OSPF will use the numerically highest IP address as Router ID, unless you manually configure the Router ID under OSPF process).

Lastly, all routers will ALWAYS list their active interfaces in the routing table with a "C" on the left-most side of the route table output. In most cases, the routers will list both the interface's subnet as well as the local addresses (the latter as /32 network).

HTH.

New Member

Re: OSPF

Also If you have not included the route for loopback on Rtr A to be advertised through Serial interface, there would be nothing advertised.

New Member

Re: OSPF

config's are necessary here...

New Member

Re: OSPF

Hi,

Let me explain /32 mask called " Host Route "

in the sense that Route for the particular host not for the network in which that paricular IP belongs ( DV protocols will do summarization in such manner only).In the case of Routers generally we can't keep the host entry becoz the Routing Table size will be unimaginable if u do so. But for Ospf/Bgp

protocols loopback addresses are execptional from this.

Incase of Router A Routing table entry check

the configuration of Router B whether you properly Advertise the networks.

Hope this helps. Pls revert back to this.

Regards

Ravi Appadurai

108
Views
0
Helpful
6
Replies
CreatePlease to create content