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BGP (finite state machine (IDLE: No route to peer, ACTIVE: No route to…
BGP
finite state machine
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ACTIVE: No route to peer
config error, possibly update source
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Flapping IDLE/ESTABLISHED
bad update, TCP MSS size in multi-hop
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Verify Configuration
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Local ASN:
for iBGP local ASN and remote ASN are same
Remote ASN:
EBGP, check if correct ASN are set
ebgp-multihop:
when source interface is used.
router checks connected interfaces by def.
you can disable it by
neighbor x.x.x.x disable connectivity check
Authentication
MD5:
creates hash, match on both sides
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Packet Drops
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If input QOS policing is confiured,
Treat control plane seperately
Verify ACLS:
Router:
if any filtering device present, similar to acls below
permit tcp host x.x.x.x host y.y.y.y eq bgp
permit tcp host x.x.x.x eq bgp host y.y.y.y
Firewall:
access-list acl-out extended permit tcp any eq bgp any
access-list acl-out extended permit tcp any any eq bgp
Notification Codes:
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consists of error code, sub-code, data portion
refer RFC for error code
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verify connections:
state should be ESTABLISHED
show tcp brief
show sockets connection tcp (NX)
telnet y.y.y.y 179 /source-interface lo0
if connection timed-out its good.
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High CPU:
100/90 , 100 is present cpu
and 90 is interrupts which means traffic
it happens if traffic is software switched.
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High CPU BGP
BGP Process in IOS:
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BGP CONSISTENCY
consistency of routing table, next hop
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BGP VA
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FIB Suppression, not loading prefixes in FIB, for which
it is not responsible.
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Solution
If BGP routes are flapping,
implement dampening
if link flapping,
implement ip event dampening
BGP Table Version
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show bgp ipv4 unicast summary
shows two versions, one is bgp table version,
other is RIB version