Introduction:
EIGRPv6 is an IPv6 routing protocol that was added to Cisco IOS starting with version 12.4T.It mimics the functionality and convergence algorithm of IPv4 EIGRP protocol and many configuration commands are similar to IPv4.To know more about EIGRPv6 please refer IP Routing: EIGRP Configuration Guide. In this document you will learned EIGRPv6 route filtering. As you know EIGRP is advance distance vector routing protocol, EIGRP running router can advertise routes to its neighbor only when they are best i.e. they should be present in routing table.
EIGRP can be configured to filter traffic using two ways;
1) Use prefix list and the distribute-list command under EIGRP process.(Traditional way of route filtering)
2) Use a route map and the distribute-list command (Advance method and give more flexible options .It was added to Cisco IOS starting with release 15M & T).
For simplicity, this document is divided into two parts. In part - 1 you will learned EIGRPv6 route filtering using prefix list and the distribute-list command under EIGRP process.
Background:
In the following topology
1) R1 configured with two LAN subnets:
2001::/64 & 2002::/64
2) R3 configured with two LAN subnets:
3001::/64 & 3002::/64
3)We will configure Route filtering on R2
Route filtering can be configured inbound or outbound:
1) When you apply filter to inbound direction, configured router will filter those routes from its routing table and as result, it will not going to advertise to neighbors.
2) When you apply filter to outbound direction, Configured router simply stop advertising these routes to its neighbor but will not affect its own routing table, these filtered routes still present in its routing table.
Topology Diagram:
Initial Configuration:
R1R2R3
interface FastEthernet1/0 ip address 1.1.1.1 255.255.255.0 ipv6 address 2001::1/64 ipv6 eigrp 10 ! interface FastEthernet1/1 no ip address ipv6 address 2002::1/64 ipv6 eigrp 10 ! interface FastEthernet0/0 ipv6 address FE80::1 link-local ipv6 eigrp 10 ! ipv6 unicast-routing ! ipv6 router eigrp 10 no shutdown | interface Loopback0 ip address 2.2.2.2 255.255.255.255 ! interface FastEthernet0/0 ipv6 address FE80::2 link-local ipv6 eigrp 10 ! interface FastEthernet0/1 ipv6 address FE80::2 link-local ipv6 eigrp 10 ! ipv6 unicast-routing ! ipv6 router eigrp 10 no shutdown | interface FastEthernet1/0 ip address 3.3.3.3 255.255.255.0 ipv6 address 3001::1/64 ipv6 eigrp 10 ! interface FastEthernet0/0 ipv6 address 3002::1/64 ipv6 eigrp 10 ! interface FastEthernet0/0 ipv6 address FE80::1 link-local ipv6 eigrp 10 ! ipv6 unicast-routing ! ipv6 router eigrp 10 no shutdown |
The following output of R1, R2 and R3 shows routes being propagated in their respective routing table via EIGRPv6.
R1#sh ipv6 route eigrp | beg D
D - EIGRP, EX - EIGRP external
D 3001::/64 [90/435200]
via FE80::2, FastEthernet0/0
D 3002::/64 [90/435200]
via FE80::2, FastEthernet0/0
R2#sh ipv6 route eigrp | beg D
D - EIGRP, EX - EIGRP external
D 2001::/64 [90/409600]
via FE80::1, FastEthernet0/0
D 2002::/64 [90/409600]
via FE80::1, FastEthernet0/0
D 3001::/64 [90/409600]
via FE80::1, FastEthernet0/1
D 3002::/64 [90/409600]
via FE80::1, FastEthernet0/1
R3#sh ipv6 route eigrp | beg D
D - EIGRP, EX - EIGRP external
D 2001::/64 [90/435200]
via FE80::2, FastEthernet0/0
D 2002::/64 [90/435200]
via FE80::2, FastEthernet0/0
Case 1 : In first case we will put filter to controll outbound direction traffic.
First you need to configure prefix list and then apply prefix list under EIGRPv6 process as shown below:
R2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R2(config)#ipv6 router eigrp 10
R2(config-rtr)#distribute-list prefix-list EIGRP_FILTER out
R2(config-rtr)#end
R2#
Verification: The following output of R1, R2 and R3 routing table shows R2 doesn’t advertise to 2001: 1/64 prefix to its neighbor i.e. R3 but not affected its own routing table.
R1#sh ipv6 route eigrp | beg D
D - EIGRP, EX - EIGRP external
D 3001::/64 [90/435200]
via FE80::2, FastEthernet0/0
D 3002::/64 [90/435200]
via FE80::2, FastEthernet0/0
R2#sh ipv6 route eigrp | beg D
D - EIGRP, EX - EIGRP external
D 2001::/64 [90/409600]
via FE80::1, FastEthernet0/0
D 2002::/64 [90/409600]
via FE80::1, FastEthernet0/0
D 3001::/64 [90/409600]
via FE80::1, FastEthernet0/1
D 3002::/64 [90/409600]
via FE80::1, FastEthernet0/1
R3#sh ipv6 route eigrp | beg D
D - EIGRP, EX - EIGRP external
D 2002::/64 [90/435200]
via FE80::2, FastEthernet0/0
Case 2 : Now we will remove applied distribution-list and apply same prefix list to inbound direction
R2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R2(config)#ipv6 router eigrp 10
R2(config-rtr)#no distribute-list prefix-list EIGRP_FILTER out
R2(config-rtr)#distribute-list prefix-list EIGRP_FILTER in
R2(config-rtr)#end
Verification:The following output of R2 and R3 routing table shows R2 doesn’t advertise to 2001: 1/64 prefix to its neighbor i.e. R3 but also filtered from its routing table.
R2#sh ipv6 route eigrp | beg D
D - EIGRP, EX - EIGRP external
D 2002::/64 [90/409600]
via FE80::1, FastEthernet0/0
D 3001::/64 [90/409600]
via FE80::1, FastEthernet0/1
D 3002::/64 [90/409600]
via FE80::1, FastEthernet0/1
R3#sh ipv6 route eigrp | beg D
D - EIGRP, EX - EIGRP external
D 2002::/64 [90/435200]
via FE80::2, FastEthernet0/0
