Brocade Multi-Service IronWare Routing Configuration Guide (Supporting R05.6.00) - Manual (Page 40)

12 Multi-Service IronWare Routing Configuration Guide
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BGP4 Restart
If the active management module fails due to a fault, the management module does not have the
opportunity to reset BGP4 sessions with neighbors as described for intentional failovers, and
illustrated in
Figure 2 . In this situation the management module will reboot, or the standby
management module becomes the new active management module. Since the new active
management module does not have the TCP/BGP4 information needed to reset the previous
sessions, a remote BGP4 peer session is only reset when it sends a BGP4/TCP keep-alive packet to
this device, or when the BGP4 hold-time expires.
To help reduce the reconnection time after a management module failover or system reload, if an
incoming TCP packet contains an MD5 digest, and no matching TCP session is found, the device
attempts to find a matching BGP4 peer based on the IP address. If a BGP4 peer configuration can
be found, the device looks up the MD5 password configured for the peer, and uses it to send a
RESET packet.
BGP4 neighbor local AS
This feature allows you to configure a device so that it adds a peer to an AS that is different from
the AS to which it actually belongs. This feature is useful when an ISP is acquired by another ISP. In
this situation, customers of the acquired ISP might not want to (or might not be able to) adjust their
configuration to connect to the AS of the acquiring provider.
For example, in Figure 3 , Customer C is connected to ISP-A which is in AS 100 and ISP-B which is in
AS 200.
FIGURE 3 Example of customer connected to two ISPs
In the example shown in Figure 4 , ISP-A has purchased ISP-B. The AS associated with ISP-B
changes to AS 100. If Customer C cannot or does not want to change their configuration or peering
relationship with ISP-B, a peer with Local-AS configured with the value 200 can be established on
ISP-B.