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Presentation_ID
46
Z
/z
AS X
AS Y
iBGP
eBGP
Y2
Y3
Y1
X1
X5
X4
X3
X2
BGP PIC – failure example
If X4 node or X1-X4 link fail …
IGP converges and now the best
IGP path to X2 is via X5
Instead of writing 250k BGP
changes, we only need to change
the ONE non-recursive LDI table,
which is to replace X4/interface
with X5/interface
O(1) vs. O(n) convergence for BGP
Non-Recursive
Prefix Leaf
X2
recursive
via X2
via X5
TenGig 1/0/1/0 Output I/F
Linecard Hardware FIB structures
this used to be X4!
In-place modification
to be X5
Recursive
Prefix Leaf
Z1 … Z250,000
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