network cisco ccna gns3 certification arteq

network cisco ccna gns3 certification arteq
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Sunday, September 30, 2012

cookbook ospf 2...

remove ospf from the interfaces... add network statements...

with ospf you can filter lsa's in but not out, unless you filter all of them out... but you love lsa's so don't do that...

r2#sh ip route ospf

Gateway of last resort is not set is subnetted, 1 subnets
O [110/2] via, 00:00:49, FastEthernet0/0

r2#sh access-list 1
Standard IP access list 1
    10 deny (2 matches)
    20 permit any
r2#sh run | beg router
router ospf 1
 network area 0
 distribute-list 1 in FastEthernet0/0

r2#sh ip route ospf
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       + - replicated route, % - next hop override

Gateway of last resort is not set

r2(config-router)#distribute-list 1 out f0/0
% Interface not allowed with OUT for OSPF

r2(config-router)#no access-list 1
r2(config)#do sh ip route ospf

Gateway of last resort is not set is subnetted, 1 subnets
O [110/2] via, 00:00:09, FastEthernet0/0

so be careful here, and listen to the cook:

It's important to remember that unlike EIGRP and RIP, OSPF uses a link state rather than a distance vector algorithm. One place where this difference becomes clear is in route filtering. At a minimum, every router in an area must see the LSAs for every other router in the same area. Depending on the type of area, it may also see summary LSAs representing routing information from other areas or other autonomous systems. These LSA packets are flooded throughout the area, with each router forwarding LSA information on to any downstream devices. Every router then separately computes the best routing table based on this link state information.
If you prevented a router from forwarding some of the LSA information, its downstream routers would not have a full link state database, and consequently wouldn't be able to generate an accurate routing table.

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