From: Jonathan V Hays (jhays@jtan.com)
Date: Thu Mar 20 2003 - 13:05:39 GMT-3
Hunt,
R2 can reach R1 via 137.20.20.1 in area 2. R1 tells R2 that its router
ID is 11.1.1.1, which goes into the OSPF database as a label to refer to
R1. Thus, you don't need a route to 11.1.1.1 in R2's routing table to
form the virtual link because 11.1.1.1 is just a known label with which
to refer to R1.
In other words, when you create the virtual link, the R2 OSPF process
knows via the OSPF Database that 11.1.1.1 is the label for R1, which it
can reach via 137.20.20.1.
HTH
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
> Behalf Of Hunt Lee
> Sent: Thursday, March 20, 2003 8:17 AM
> To: ccielab@groupstudy.com
> Subject: Trunk mystery
>
>
> Hi group,
>
> I'm confused on the following eg.
>
> <--- Area 2 ----->
>
> Trunk VLAN30
> 11.1.1.1---R1 --- Cat 3550 ---- R2---200.200.200.1
> (Area 11) |
> |
> |
> other OSPF routers (OSPF Area 0)
>
> R2 is advertising a default route out to OSPF
> by: ip route 0.0.0.0 0.0.0.0 137.20.20.2
>
> Both 11.1.1.1 & 200.200.200.1 are Loopback interface by R1
> and R2 respectively
>
> I scratched my head as to how can R2 establish a virtual-link
> to R1 with IP 11.1.1.1, where 11.1.1.1 is in Area 11, since I
> was expecting that R2 won't be able to know about 11.1.1.1
> until the Virtual-Link is formed...
>
> At R2:-
>
> interface Loopback0
> ip address 200.200.200.1 255.255.255.0
>
> interface Ethernet0
> ip address 137.20.20.1 255.255.255.0
> ip ospf priority 200
>
> router ospf 1
> router-id 200.200.200.1
> log-adjacency-changes
> area 2 virtual-link 11.1.1.1 <---- How can R2 see 11.1.1.1
> network 137.20.20.1 0.0.0.0 area 2
> network 150.100.32.2 0.0.0.0 area 0
> default-information originate metric 100 metric-type 1
>
> At R1:-
>
> interface Loopback0
> ip address 11.1.1.1 255.255.255.0
>
> interface FastEthernet0/0.1
> encapsulation dot1Q 10
> ip address 192.168.1.11 255.255.255.224
> !
> interface FastEthernet0/0.2
> encapsulation dot1Q 20
> ip address 10.90.1.11 255.255.255.0
> !
> interface FastEthernet0/0.3
> encapsulation dot1Q 30
> ip address 137.20.20.11 255.255.255.0
> !
> router ospf 1
> router-id 11.1.1.1
> log-adjacency-changes
> area 2 virtual-link 200.200.200.1
> summary-address 192.168.1.0 255.255.255.0
> network 11.1.1.1 0.0.0.0 area 11
> network 137.20.20.11 0.0.0.0 area 2
>
>
> And at 3550:-
>
> interface FastEthernet0/2
> description R2
> switchport access vlan 30
> switchport mode access
> no ip address
>
> interface FastEthernet0/14
> description R1's Trunk port
> switchport trunk encapsulation dot1q
> switchport trunk allowed vlan 1-39,184-4094
> switchport mode trunk
> no ip address
> duplex full
> speed 100
>
> Regards,
> Lee
>
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This archive was generated by hypermail 2.1.4 : Sat Apr 05 2003 - 08:51:42 GMT-3