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:
R1
|
R2
|
R3
|
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
