SRLGs in Inter-Area LSPs

05.12.12   |  
‎05-12-2012 06:35 AM

Hi All,


Just wondering if SRLGs are carried through between IGP areas, both for OSPF and for IS-IS?


The scenario for this would be passing a cspf routed RSVP LSP from PE1 in Area 1 through to PE2 in Area 2.  We would maintain a secondary standby LSP path for this traffic with exclude-srlg enabled.

Assuming that the primary path takes the IGP routed path PE1 - ABR1 - ABR3 - PE2 then the secondary path will take the path PE1 - ABR2 - where?

If SRLGs are carried through by the IGP then then the path should go PE1 - ABR2 - ABR4 - PE2, however if the SRLGs are not carried through then the IGP could in make the secondardy path PE1 - ABR2 - ABR3 - PE2 which obviously is not a great standby secondary path...


       /--- ABR1 ---|             |--- ABR3 ---\

PE1  (Area1)      | Area 0 |      (Area2)  PE2

       \--- ABR2 ---|             |--- ABR4 ---/


If anybody knows this scenario and can shed some insight it would be greatly appreciated Smiley Happy