RIP: Configuring off-set list
·
We
can use off-set list in RIP to change the metric
·
Let
me take a small topology to configure offset-list in RIP
R1------S1/0-------------s1/0----R2----s1/1--------------s1/1------R3
10.1.12.1--------------10.1.12.2-----11.1.23.2--------------11.1.23.3
R1(config-router)#do
show run | sec router
router
rip
version 2
network 1.0.0.0
network 10.0.0.0
no auto-summary
R1(config-router)#
R2(config-router)#do
show run | sec router
router
rip
version 2
network 2.0.0.0
network 10.0.0.0
no auto-summary
R2(config-router)#
R1(config-router)#do
show ip route
Codes:
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
Gateway
of last resort is not set
1.0.0.0/32 is subnetted, 1 subnets
C 1.1.1.1 is directly connected, Loopback0
2.0.0.0/32 is subnetted, 1 subnets
R 2.2.2.2 [120/1] via 10.1.12.2, 00:00:26,
Serial1/0
10.0.0.0/24 is subnetted, 1 subnets
C 10.1.12.0 is directly connected,
Serial1/0
R1(config-router)#
R2(config-router)#do
show ip route
Codes:
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
Gateway
of last resort is not set
1.0.0.0/32 is subnetted, 1 subnets
R 1.1.1.1 [120/1] via 10.1.12.1, 00:00:26,
Serial1/0
2.0.0.0/32 is subnetted, 1 subnets
C 2.2.2.2 is directly connected, Loopback0
10.0.0.0/24 is subnetted, 1 subnets
C 10.1.12.0 is directly connected,
Serial1/0
11.0.0.0/24 is subnetted, 1 subnets
C 11.1.23.0 is directly connected,
Serial1/1
R2(config-router)#
Observation:
·
RIP
is configured between R1 and R2
·
R1
has advertised its loopback0 1.1.1.1/32 into RIP
·
R2
has R1’s loopback0 with RIP metric 1
·
R2
has advertised its loopback0 2.2.2.2/32 into RIP
·
R1
has R2’s loopback0 with RIP metric 1
·
Now,
let me configure off-set list to change the metric:
R1(config)#access-list
1 permit 1.1.1.1
R1(config)#router
rip
R1(config-router)#offset-list
1 out ?
<0-16>
Offset
R1(config-router)#offset-list
1 out 10
R1(config-router)#
Observation:
·
Now,
offset-list is configured in such a way that when R2 sees the route match by
access-list 1, it should add 10 to the original metric.
·
That
means if we check R2’s routing table now, R2 should see this route as metric 11
·
Let
me check this from R2:
R2(config-router)#do show ip route
Codes:
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
Gateway
of last resort is not set
1.0.0.0/32 is subnetted, 1 subnets
R
1.1.1.1 [120/11] via 10.1.12.1, 00:00:06, Serial1/0
2.0.0.0/32 is subnetted, 1 subnets
C 2.2.2.2 is directly connected, Loopback0
10.0.0.0/24 is subnetted, 1 subnets
C 10.1.12.0 is directly connected,
Serial1/0
11.0.0.0/24 is subnetted, 1 subnets
C 11.1.23.0 is directly connected,
Serial1/1
R2(config-router)#
Observation:
·
Yes,
R2 has this R1’s loopback 1.1.1.1/32 as Metric 11
·
I
have configured this in R1 out as of now
·
But,
Depending on the requirement, we can configure as in or out.
·
If
I have to configure it in R2, then I need to configure as in.
·
Let
me configure in R2 now:
R1(config-router)#no
offset-list 1 out 10
R2(config-router)#access-list
1 permit 1.1.1.1
R2(config)#router
rip
R2(config-router)#offset-list
1 in 11
R2(config-router)#
Observation:
·
Now,
offset-list is configured in such a way that when R2 sees the route match by
access-list 1, it should add 11 to the original metric.
·
That
means if we check R2’s routing table now, R2 should see this route as metric 12
·
Let
me check this from R2:
R2(config-router)#do show ip route
Codes:
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
Gateway
of last resort is not set
1.0.0.0/32 is subnetted, 1 subnets
R
1.1.1.1 [120/12] via 10.1.12.1, 00:00:17, Serial1/0
2.0.0.0/32 is subnetted, 1 subnets
C 2.2.2.2 is directly connected, Loopback0
10.0.0.0/24 is subnetted, 1 subnets
C 10.1.12.0 is directly connected,
Serial1/0
11.0.0.0/24 is subnetted, 1 subnets
C 11.1.23.0 is directly connected,
Serial1/1
R2(config-router)#
Observation:
·
Yes,
R2 has this R1’s loopback 1.1.1.1/32 as Metric 12
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