[j-nsp] SRLGs in Inter-Area LSPs

[Caillin Bathern]

Hi All,

 

I posted this to the J-Net forums but no luck.

 

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 secondary 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.

Cheers,

Caillin