Information Technology Reference
In-Depth Information
In some scenarios, TX-side loop detection is undesirable—specifically, in MPLS-VPN
environments. This used to be the default behavior when peer groups were not used;
however, it was removed for MPLS-VPN support.
NOTE
Outbound Route Filtering
The BGP ORF feature uses BGP ORF send and receive capabilities to minimize the number
of BGP updates sent between peer routers. Configuring this feature can help reduce the
number of resources required for generating and processing routing updates by filtering
unwanted routing updates on the transmit side.
The BGP ORF feature is enabled through the advertisement of ORF capability to BGP peer
routers. This capability indicates that a BGP-speaking router accepts a prefix list from a
neighbor and applies the prefix list outbound to that peer. The BGP ORF feature can be
configured with send, receive, or send and receive ORF capabilities. The BGP router
continues to apply the inbound prefix list to received updates after the BGP router has
pushed the inbound prefix list to the remote peer.
A sample configuration is provided in Example 3-14.
Example 3-14
BGP ORF Capability Configuration
router bgp 100
...
neighbor 10.1.1.1 remote-as 10
neighbor 10.1.1.1 capability prefixlist-orf both
...
!
In Example 3-14, the BGP ORF advertises the capability with both the send and receive
options. Instead of the
both
keyword, either
send
or
receive
can be used to allow one-way
ORF. The
send
and
receive
keywords indicate the ability to send or receive the prefix list.
They do not refer to the advertisement of routes.
The BGP ORF feature cannot be used with BGP peer groups when a peer group member is
receiving a prefix list. The dynamic nature of the outbound policy prevents update replica-
tion. Peer group members can send policies. The BGP ORF capability was introduced in
Releases 12.0(6)S and 12.0(7)T.
Case Study: BGP Convergence Testing
The topic of BGP convergence tuning was covered earlier in this chapter. The discussion
examined the bottlenecks in the BGP update process and presented configuration options
