Cabletron Systems SmartSwitch Router 9032578-02 - Manual (Page 78)

Chapter 6: BGP Configuration Guide
78 SmartSwitch Router User Reference Manual
Notes on Using the AS Path Prepend Feature
• Use the as-count option for external peer-hosts only.
• If the as-count option is entered for an active BGP session, routes will not be resent to
reflect the new setting. To have routes reflect the new setting, you must restart the peer
session. To do this:
a. Enter Configure mode.
b. Negate the command that adds the peer-host to the peer-group. (If this causes the
number of peer-hosts in the peer-group to drop to zero, then you must also
negate the command that creates the peer group.)
c. Exit Configure mode.
d. Re-enter Configure mode.
e. Add the peer-host back to the peer-group.
If the as-count option is part of the startup configuration, the above steps are
unnecessary.
BGP Configuration Examples
This section presents sample configurations illustrating BGP features. The following
features are demonstrated:
• BGP peering
• Internal BGP (IBGP)
• External BGP (EBGP) multihop
• BGP community attribute
• BGP local preference (local_pref) attribute
• BGP Multi-Exit Discriminator (MED) attribute
• EBGP aggregation
• Route reflection
BGP Peering Session Example
The router process used for a specific BGP peering session is known as a BGP speaker. A
single router can have several BGP speakers. Successful BGP peering depends on the
establishment of a neighbor relationship between BGP speakers. The first step in creating