Virtual Links and Partitioned Areas ..


IS-IS

– IS-IS allows a Level-1 Area which is partitioned to be automatically repaired, by electing Partition Designated Level 2 routers and having a virtual link between them. The mechanism is not often implemented and requires an explicit tunnelling mechanism.
             
– Used in ISO IS-IS for connecting partitions of Level 1 Area over the Level 2 backbone.   
             
OSPF   
        
– Used for connecting physically separate area zeroes (0.0.0.0) to maintain contiguity of the backbone.

– Used for connecting remote areas to the backbone through other areas if direct physical connectivity is not possible. This enables an OSPF packet to be sent from one part of an remote isolated site to the main OSPF network.   
          
– For Virtual links to work, OSPF accepts packets which are have originated more than one hop away. This can lead to security concerns if the packets at the edge of the domain are not properly filtered.  

Advertisements

About Manav Bhatia

Manav Bhatia is a SDN/NFV dataplane architect at Ionos Networks and has co-authored several IETF standards on routing protocols, BFD, IPv6, security, etc. He is also a member of IETF Routing Area Directorate where he helps the Area Directors review the IETF standards for their impact on the Routing Area. View all posts by Manav Bhatia

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: