Configuring route flap dampening – Brocade BigIron RX Series Configuration Guide User Manual

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BigIron RX Series Configuration Guide

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Filtering

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Syntax: show ip bgp neighbor <ip-addr>

To display the ORFs received from a neighbor, enter a command such as the following.

Syntax: show ip bgp neighbor <ip-addr> received prefix-filter

Configuring route flap dampening

A “route flap” is the change in a route’s state, from up to down or down to up. When a route’s state
changes, the state change causes changes in the route tables of the routers that support the route.
Frequent changes in a route’s state can cause Internet instability and add processing overhead to
the routers that support the route.

Route flap dampening is a mechanism that reduces the impact of route flap by changing a BGP4
router’s response to route state changes. When route flap dampening is configured, the device
suppresses unstable routes until the route’s state changes reduce enough to meet an acceptable
degree of stability. The Brocade implementation of route flap dampening is based on RFC 2439.

Route flap dampening is disabled by default. You can enable the feature globally or on an
individual route basis using route maps.

NOTE

The BigIron RX applies route flap dampening only to routes learned from EBGP neighbors.

BigIron RX# show ip bgp neighbor 10.10.10.1

1 IP Address: 10.10.10.1, AS: 65200 (IBGP), RouterID: 10.10.10.1

State: ESTABLISHED, Time: 0h0m7s, KeepAliveTime: 60, HoldTime: 180

RefreshCapability: Received

CooperativeFilteringCapability: Received

Messages: Open Update KeepAlive Notification Refresh-Req

Sent : 1 0 1 0 1

Received: 1 0 1 0 1

Last Update Time: NLRI Withdraw NLRI Withdraw

Tx: --- --- Rx: --- ---

Last Connection Reset Reason:Unknown

Notification Sent: Unspecified

Notification Received: Unspecified

TCP Connection state: ESTABLISHED

Byte Sent: 110, Received: 110

Local host: 10.10.10.2, Local Port: 8138

Remote host: 10.10.10.1, Remote Port: 179

ISentSeq: 460 SendNext: 571 TotUnAck: 0

TotSent: 111 ReTrans: 0 UnAckSeq: 571

IRcvSeq: 7349 RcvNext: 7460 SendWnd: 16384

TotalRcv: 111 DupliRcv: 0 RcvWnd: 16384

SendQue: 0 RcvQue: 0 CngstWnd: 5325

BigIron RX# show ip bgp neighbor 10.10.10.1 received prefix-filter

ip prefix-list 10.10.10.1: 4 entries

seq 5 permit 10.10.0.0/16 ge 18 le 28

seq 10 permit 20.20.10.0/24

seq 15 permit 30.0.0.0/8 le 32

seq 20 permit 40.10.0.0/16 ge 18

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