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Webcast-Catalyst9k
New Member

Several loopback Addresses

Hi,

One of my router configured with 4 loopback addresses and advertised in OSPF.My question is as per my knowledge, if you have more than one loopback addresses configured on router then it select as router ID based on highest ip address. then what does it make sense to configure so many LB addresses instead of one as well to advertise them into OSPF.

3 REPLIES
Hall of Fame Super Silver

Re: Several loopback Addresses

Hello Farook,

>> what does it make sense to configure so many LB addresses instead of one as well to advertise them into OSPF.

There are some possible reasons/usage for multiple loopbacks on same device:

- clearly in a lab environment they serve as test networks

- in a production environment a loopback can be used as the next-hop for one kind of services in MPLS TE environments combining iBGP, OSPF and MPLS TE so multiple services can mean multiple loopbacks.

- in some networks administrators want to use different loopbacks as Router-ids of different protocols and/or one loopback is used for management purposes

About router-ids of different protocols successful redistribution of OSPF into BGP requires that they share the same router-id.

Hope to help

Giuseppe

Hall of Fame Super Gold

Re: Several loopback Addresses

farook

Perhaps another scenario where you might want multiple loopback interfaces configured and advertised into OSPF might be that you are configuring a pool of addresses to use with Remote Access VPN or Remote Access Services/Dial Access. You want the subnet of the address pool advertised into your network so that devices in your network have routes to this pool of addresses. An easy way to do this is to configure another loopback interface on the router (in addition to the loopback used as the RID for OSPF) and to give the extra loopback an address in the subnet of the pool, and to have a network statement in OSPF matching the extra loopback.

HTH

Rick

New Member

Re: Several loopback Addresses

Thank you,

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