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ROUTING

EXCELLENT

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GUESTBOOK

43. Select and configure the different ways to control routing update traffic

Redistribution guidelines

1. Be familiar with the network and it's traffic
2. Not to overlap routing protocols
3. One/two-way Redistribution

Selecting the best route parameters

1. Administrative distance (believability)
2. Routing metric

Protocol redistribution consideration

1. Support the same routed protocol stack
2. Redistribution varieties between protocols

EIGRP redistribution consideration

1. IGRP & EIGRP redistribution is automatic only in the same AS
2. Automatically redistribute IPX RIP. Can be configured to redistribute NLSP since IOSV11.1
3. Automatically redistribute AT RTMP.
4. Configure redistribution for all other IP routing protocol.

Local preference is for setting a preferred outbound-pathway for the originating AS when redundancy is enabled.

MED is for setting a preferred return pathway back into the origination AS.

Ways to control routing update traffic:

1. Passive interface (PI)
   • Continue receiving DV updates
   • Stop sending DV updates
   • Prohibit LS routing protocols to form adjacencies by blocking the hello packets
   • Applies to all IP-based routing protocols except the BGP.
   • In OSPF, PI is a stub network in the domain.
   • In EIGRP, PI stops router sending hello packets, so the route filters should be applied out of the interface.
   router(config-router)#passive-interface type number
2. Default routes, used when the router doesn't have a route for a given destination.
   router(config)#ip default-network network-number
   router(config)#ipx advertised-default-route-only network
3. Static routes, a route to a destination configured statically.
   1. By a next hop address if there is a route address.
      • Redistribution required.
      • Default administrative distance is 1.
      router(config)#ip route network mask {next hop address} [administrative distance]
   2. By an interface if there is no route to the next hop address.
      • Automatically redistributed.
      • Default administrative distance is 0.
      router(config)#ip route network mask {out interface} [administrative distance]
4. Route filters, using the access lists to filter specific routing update by applying it to a routing protocol and / or an interface.
   router(config)#access-list access-list-number deny any
   router(config-router)#distribute-list access-list-number in | out [interface-name]