35-49
Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
OL-9639-07
Chapter 35 Configuring IP Unicast Routing
Configuring BGP
There are two types of reset, hard reset and soft reset. The switch supports a soft reset without any prior
configuration when both BGP peers support the soft route refresh capability, which is advertised in the
OPEN message sent when the peers 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
local 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.
Beginning in privileged EXEC mode, follow these steps to learn if a BGP peer supports the route refresh
capability and to reset the BGP session:
Ta b l e 35-10 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
provided by the neighbor are lost. Not
recommended.
Outbound soft reset No configuration, no storing of routing table
updates
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
and has no memory overhead
Both BGP routers must support the route
refresh capability.
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.
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