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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