Caution
Enabling multihop BGP connections is dangerous because BGP speakers might establish a BGP connection through a
|
|
|
|
|
|
|
|
| AS1 |
|
|
|
| AS2 | ||
|
|
|
| Nokia |
|
| Nokia | |||||||||
|
|
|
| EBGP | Platform B |
| ||||||||||
| Platform A |
| ||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Loopback | Loopback | |
Address | ||
Address | ||
| ||
| 00330 |
Router A and Router B are connected by two parallel serial links. To provide fault tolerance and enable
Route Dampening
Route dampening lessens the propagation of flapping routes. A flapping route is a route that repeatedly becomes available then unavailable. Without route dampening, autonomous systems continually send advertisement and withdrawal messages each time the flapping route becomes available or unavailable. As the Internet has grown, the number of announcements per second has grown as well and caused performance problems within the routers.
Route dampening enables routers to keep a history of the routes that are flapping and prevent them from consuming significant network bandwidth. This is achieved by measuring how often a given route becomes available and then unavailable. When a set threshold is reached, that route is no longer considered valid, and is no longer propagated for a given period of time, usually about 30 minutes. If a route continues to flap even after the threshold is reached, the time out period for that route grows in proportion to each additional flap. Once the threshold is reached, the route is dampened or suppressed. Suppressed routes are added back into the routing table once the penalty value is decreased and falls below the reuse threshold.
Route dampening can cause connectivity to appear to be lost to the outside world but maintained on your own network because route dampening is only applied to BGP routes. Because of increasing load on the backbone network routers, most NSPs (MCI, Sprint, UUNet etc.) have set up route suppression.
TCP MD5 Authentication
The Internet is vulnerable to attack through its routing protocols and BGP is no exception. External sources can disrupt communications between BGP peers by breaking their TCP connection with spoofed RST packets. Internal sources, such as BGP speakers, can inject bogus routing information from any other legitimate BGP speaker. Bogus information from either external or internal sources can affect routing behavior over a wide area in the Internet.
Nokia Network Voyager for IPSO 4.0 Reference Guide | 411 |
