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what is the need of overload bit ??? i know DN , domain-tag , P bit

Ibrahim Jamil
Level 6
Level 6
Hi what is the need of overload bit ??? i know DN , domain-tag , P bit thanks all
3 Replies 3

Giuseppe Larosa
Hall of Fame
Hall of Fame

Hello Ibrahim,

the overload bit was introduced in ISIS as a way for an ISIS speaking router to signal it should not be used as a transit router as it is or out of resources or it is stlll converging.

 

All the other bits you mention are related to OSPF.

An OSPF router can become not-transit if using the command  max-metric router-lsa under router ospf.

 

However, other OSPF implementations may set "the overload bit for OSPF" also

see the following thread that mentions a command for Juniper routers

 

https://community.cisco.com/t5/routing/ospf-overload/td-p/631715

 

Edit:

Actually also the Juniper implementations increases the metric of links in routers LSA to 65535

see

>> A timer is started for the difference between the timeout and the time elapsed since the instance started. When the timer expires, overload mode is cleared. In overload mode, the router link-state advertisement (LSA) is originated with all the transit router links (except stub) set to a metric of 0xFFFF. 

 

https://www.juniper.net/documentation/en_US/junos/topics/concept/ospf-overload-function-overview.html

 

I would say that setting the overload bit in OSPF is actually the same as using the max-metric router-lsa command in Cisco Routers.

 

Hope to help

Giuseppe

 

thanks Giuseppe

BitcoinTidings
Level 1
Level 1

Well explained, I searched for a long time about the overload bit. It is explained very simply here.

 

Thanks

 

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