Route redistribution knowledge points
I. Route redistribution
The protocol features that have the greatest impact on redistribution are differences in metric and administrative distance, as well as protocol categories.
Ignoring these differences will cause problems such as routing loops, black holes, switching failures, and so on.
The default situation for redistribution without Mtricl value is as follows:
Agreement
SeedMetricRIP
Infinity
Must be specified manually
EIGRP
Infinity must also specify OSPF manually
20IS-IS
0BGP
Carry the original Metricvalue
The ospf declaration must have a sub, otherwise the subnet cannot receive it.
Route summary benefits: reduce routing table, save memory and CPU, disadvantages: reduced accuracy, increased error routing
Second, route filtering
Distribute-list controls the information in the routing table-distribution list (mainly applies distance vector protocols Rip and Eigrp)
Distribute-list can only be used with standard ACL, prefix-list and route-map, but not with extended ACL.
Filter-list
First, path filtering (filter-list), mainly combined with the regular expression of bgp is used in as-path filtering.
Second, filter-list is aimed at filtering in the process of summarizing lsa1/lsa2 into LSA3 on ABR
Ip as-path access-list 1 deny _ 300 _ / / reject any route through AS300
Ip as-path access-list 1 permit. *
Router bgp 200
Neighbor 195.1.1.1 filter-list 1 out
Comparison of distribute-list & filter-list in ospf:
1. Distribute-list is aimed at filtering when routes are put into the routing table from the database of OSPF; the operation object is routes.
2. Filter-list is aimed at filtering in the process of summarizing lsa1/lsa2 into LSA3 on ABR; the operation object is LSA3.
Difference: distribute-list 1 in Serial1/2
1. Can only be used in in direction
2. Use either acl [Standard] or prefix/route-map.
Area 1 filter-list prefix 1 out
1, in and out in the direction
2, only prefix-list can be used
For protocol migration, it is best to reduce the administrative distance, complete the configuration of the new protocol, and modify the administrative distance again.
