BGP Policy Processing Order
Inbound
1. Route map
2. Filter list, AS-path access list, or IP policy
3. IP prefix list or Distribute list
Outbound
1. IP prefix list or Distribute-list
2. Filter list, AS-path access list, or IP policy
3. Route map
Friday, June 26, 2009
Wednesday, June 24, 2009
BGP OSPF redistribution.
1. By default, BGP only redistribute ospf network type internal. To redistribute other type of ospf network, you need to add to the redistribution
redistribute ospf 1 ------ Only internal (intra and inter-area) routes
redistribute ospf 1 match external ---- Only external type 1 and 2 route
redistribute ospf 1 match internal external 2 --- only internal and external type 2
redistribute ospf 1 match nssa-external 1 ---- Only nssa-external type 1.
2. By default, iBGP redistribution into IGP is disabled.
Issue the bgp redistribute-internal command under router bgp process in order to enable redistribution of iBGP routes into IGP.
3. BGP and OSPF router-id
If BGP synchronization is enabled, there must be a match for the prefix in the IP routing table in order for an internal BGP (iBGP) path to be considered a valid path.
4. Link for tips. 911network.
redistribute ospf 1 ------ Only internal (intra and inter-area) routes
redistribute ospf 1 match external ---- Only external type 1 and 2 route
redistribute ospf 1 match internal external 2 --- only internal and external type 2
redistribute ospf 1 match nssa-external 1 ---- Only nssa-external type 1.
2. By default, iBGP redistribution into IGP is disabled.
Issue the bgp redistribute-internal command under router bgp process in order to enable redistribution of iBGP routes into IGP.
3. BGP and OSPF router-id
If BGP synchronization is enabled, there must be a match for the prefix in the IP routing table in order for an internal BGP (iBGP) path to be considered a valid path.
4. Link for tips. 911network.
Thursday, June 11, 2009
IPv6 ACL implicit rules
IPv6 ACL Implicit Rules
• Implicit permit rules allow neighbor discovery
The following implicit rules exist at the end of each IPv6 ACL to allow ICMPv6 neighbor discovery:
permit icmp any any nd-na
permit icmp any any nd-ns
deny ipv6 any any
• Implicit permit rules allow neighbor discovery
The following implicit rules exist at the end of each IPv6 ACL to allow ICMPv6 neighbor discovery:
permit icmp any any nd-na
permit icmp any any nd-ns
deny ipv6 any any
Friday, June 05, 2009
Timer for different routing protocol
1. OSPF
Both sides must match the hello and hold timer.
For fast hello which the hello intervla is lower than 1 second, the hello is carried as 0. So the hello multipler dose not need to be match.
2. EIGRP
Two sides will exchange the hold time. It does not need to be matched. The router will use the hold time learn from the neighbor as the hold timer.
Let's say you configure R1 hello=10 Hold=60. R2 with default hello=5, hold=15.
On R1 show ip eigrp neighbor, it will should hold time 15 for R2.
On R2 show ip eigrp neighbor, it will should hold time 60 for R1.
3. BGP
Two sides will exchange the hold time. But the difference between EIGRP and BGP is, BGP will choose the small one as the hold time for both side. And if hello time is not configure, it will calculator from hold time.
Both sides must match the hello and hold timer.
For fast hello which the hello intervla is lower than 1 second, the hello is carried as 0. So the hello multipler dose not need to be match.
2. EIGRP
Two sides will exchange the hold time. It does not need to be matched. The router will use the hold time learn from the neighbor as the hold timer.
Let's say you configure R1 hello=10 Hold=60. R2 with default hello=5, hold=15.
On R1 show ip eigrp neighbor, it will should hold time 15 for R2.
On R2 show ip eigrp neighbor, it will should hold time 60 for R1.
3. BGP
Two sides will exchange the hold time. But the difference between EIGRP and BGP is, BGP will choose the small one as the hold time for both side. And if hello time is not configure, it will calculator from hold time.
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