Cisco Catalyst 3750-E - Page 1030

40-52
Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-08
Chapter 40 Configuring IP Unicast Routing
Configuring BGP
establish a TCP session. A soft reset allows the dynamic exchange of route refresh requests and routing
information between BGP routers and the subsequent re-advertisement of the respective outbound
routing table.
• When soft reset generates inbound updates from a neighbor, it is called dynamic inbound soft reset.
• When soft reset sends a set of updates to a neighbor, it is called outbound soft reset.
A soft inbound reset causes the new inbound policy to take effect. A soft outbound reset causes the new
l
ocal outbound policy to take effect without resetting the BGP session. As a new set of updates is sent
during outbound policy reset, a new inbound policy can also take effect.
Table 40-10
lists the advantages and disadvantages hard reset and soft reset.
Beginning in privileged EXEC mode, follow these steps to learn if a BGP peer supports the route refresh
c
apability and to reset the BGP session:
Ta b l e 40-10 Advantages and Disadvantages of Hard and Soft Resets
Type of Reset Advantages Disadvantages
Hard reset No memory overhead The prefixes in the BGP, IP, and FIB tables
p
rovided by the neighbor are lost. Not
recommended.
Outbound soft reset No configuration, no storing of routing table
u
pdates
Does not reset inbound routing table updates.
Dynamic inbound soft reset Does not clear the BGP session and cache
Does not require storing of routing table updates
a
nd has no memory overhead
Both BGP routers must support the route
r
efresh capability (in Cisco IOS Release 12.1
and later).
Command Purpose
Step 1
show ip bgp neighbors Display whether a neighbor supports the route refresh capability. When supported,
this message appears for the router:
Received route refresh capability from peer.
Step 2
clear ip bgp {* | address |
peer-group-name}
Reset the routing table on the specified connection.
• Enter an asterisk (*) to specify that all connections be reset.
• Enter an IP address to specify the connection to be reset.
• Enter a peer group name to reset the peer group.
Step 3
clear ip bgp {* | address |
peer-group-name} soft out
(Optional) Perform an outbound soft reset to reset the inbound routing table on the
specified connection. Use this command if route refresh is supported.
• Enter an asterisk (*) to specify that all connections be reset.
• Enter an IP address to specify the connection to be reset.
• Enter a peer group name to reset the peer group.
Step 4
show ip bgp
show ip bgp neighbors
Verify the reset by checking information about the routing table and about BGP
neighbors.