Brocade Multi-Service IronWare Routing Configuration Guide (Supporting R05.6.00) - Manual (Page 63)

Multi-Service IronWare Routing Configuration Guide 35
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Specifying a maximum AS path length
Attribute flag error (ignore the AS4_PATH)
SYSLOG: Sep 9 19:02:03:<11>mu2, BGP: From Peer 192.168.1.1 received invalid
AS4_PATH attribute flag (0x40) - entire AS4_PATH ignored
Confederation segments after AS_SEQ/AS_SET (ignore the AS4_PATH)
SYSLOG: Sep 9 19:02:03:<11>mu2, BGP: From Peer 192.168.1.1 received invalid
Confed info in AS4_PATH (@byte 43) - entire AS4_PATH ignored
Invalid segment types (ignore the AS4_ PATH)
SYSLOG: Sep 9 19:02:03:<11>mu2, BGP: From Peer 192.168.1.1 received incorrect Seq
type/len in AS4_PATH (@byte 41) - entire AS4_PATH ignored
More than one AS4_PATH (Use the first one and ignore the others)
SYSLOG: Sep 9 19:02:03:<11>mu2, BGP: From Peer 192.168.1.1 received multiple
AS4_PATH attributes - used first AS4_PATH attribute only
Specifying a maximum AS path length
You can use the maxas-limit in command to configure a router running BGP4 to discard routes that
exceed a specified AS path limit. This limit can be configured globally, for peer groups, and for BGP
neighbors.
When you configure the maxas-limit in setting, the behavior of the router changes to first check the
length of the AS paths in the UPDATE messages and then to apply the inbound policy. If the AS path
exceeds the configured length, then the router performs the following actions:
• Does not store the route in the RIB and does not forward the NLRIs and attributes contained in
the UPDATE message for that route
• Logs an error
• Processes the withdrawn NLRIs in the same update message
If a route from a peer exceeds the configured Maximum AS path limit, the router also removes the
same route from that peer, if it exists, from its own RIB.
After a maximum AS path length is configured, the maximum AS path limit applies to all new
inbound routes. To update previously stored routes, you must perform an inbound soft reset for all
of the address families activated for that particular BGP neighbor session.
NOTE
If the neighbor soft-reconfiguration feature is enabled, you must perform a hard reset on the router
to impose the maximum length limit.
NOTE
Maxas-limit is checked against the received AS_PATH and AS4_PATH attributes.
BGP routers check for and, if configured, apply the maxas-limit in setting in the following order:
1. Neighbor value
2. Peer group value
3. Global value