Hi IS-IS experts, Please provide your valuable feedback.
Regards, Venkat. On Wed, Apr 12, 2023 at 10:00 AM Venkataratnam Naidu <[email protected]> wrote: > Hello Experts, > > > > Need your opinion on how node should behave with "IS-IS summary-routes > with overload-bit start-up" > > > > Ideally when an overload-bit is set node can't be used as a transit node, > local routes still be reached using this overloaded node. With the below > topo there is some traffic black hole and looking for your inputs on how we > can avoid such issues. > > > > -- PE1 -- > > | 9| > > abr1 abr2 > > | | > > P1 ------ P2 > > |8 | > > -- PE2 -- > > > > 1. abr1 & abr2 summarizing is-is routes that received from PE1 and adding > summary routes as part of its LSP and flooding. > > 2. abr1 & abr2 has two lsp fragments lsp.0 and lsp.1 where summary routes > are present in lsp.1 > > 3. PE2 receives summary routes and chooses the active path as p1->abr1 and > backup path as p2->abr2. > > 4. when abr1 reloaded and comes up with overload-bit start-up set in boot > config, it forming adj with P1 and creates lsp.0 with over load bit and > floods > > 5. PE2 computes its SPF with abr1 new lsp.0 and old lsp.1 this results in > an active path as p1 ->abr1(after reload abr1 has not yet formed adj with > PE1 yet). This results in traffic drop at abr1 for a few milliseconds. > > 6. After a few milliseconds abr1(as part of db sync abr1 received its > lsp.1 from P1) sending purge to its lsp.1. > > 7. PE2 computes its SPF with abr1 lsp.0 and purged lsp.1 and chooses an > active path as p2->abr2, with this traffic issue being rectified. > > > > > > Regards, > > Venkat. >
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