10-19-2008 01:58 AM - edited 03-03-2019 11:59 PM
I would like to know if it is possible to force traffic through a route-map in OSPF & EIGRP within the particular area/AS so i can manupilate their cost/metric if needed ???
10-19-2008 05:44 AM
Hello Ryel,
costs and metrics are attributes of IP routes and not of user traffic.
There are some ways to influence a routing protocol decision by manipulating the cost/metric of outgoing interface.
But this cannot happen selectively using a route-map.
ospf
int type x/y
ip ospf cost OR bandwidth xxxx
EIGRP: the most secure way is to increase delay on path that is to become a backup path
take sh int type x/y read the delay value and then increase it
int type x/y
delay yyyy
If you want to influence the path for only some type of traffic:
a) route-maps in redistribution points can be used : when redistributing between two routing protocols you can use differentiated seed metric and change metric type with route-maps but this requires the usage of two routing protocols with two border routers.
b)
You can forward traffic in a selective way overriding unicast routing decisions using PBR (policy based routing)
the command is applied inbound on the interface that receives the traffic to be diverted
the route-map will use an extended ACL to define traffic to be diverted and a set action that will provide an outgoing interface or an ip next-hop (one or more used in a ordered manner)
example
access-list 121 permit tcp 10.10.10.0 0.0.0.255 any eq 80
route-map pbr_web permit 10
match ip adddress 121
set ip next-hop 10.10.20.2
int fa0/0
ip policy route-map pbr_web
notes:
if multiple rx ifs are possible the command has to be applied to all of them
traffic generated on router is not affected
if the specified next-hop/outgoing interface is not available traffic is routed normally
all traffic not matched by PBR route-map is normally routed (no discarding effects)
The effect is local to the node:
if you have to build a multi-hop alternate path you need to configure PBR on all nodes on the path
Hope to help
Giuseppe
10-19-2008 07:49 AM
Hello Giuseppe,
Thanks for replying i tried using "ip policy route-map" but was unable to get what i needed. I am sending the sh run of the 4 routers that i am currrently using kindly have a look at it and give me your input. What i want is that on R4 the loopback on R5 6.6.6.6 should be reached via 24.0.0.1 currently the primary path is through 45.0.0.2. I know this can be acheived by "ip ospf cost" but wanted to know if it can be done by route-maps. Using a route-map with a distribute list i am able to deny (i am unable to chage the metric) 6.6.6.6 via 45.0.0.2 but the path through 24.0.0.1 does not come up.
R4 s1/2 - R5 s1/2
R4 s1/1 - R2 s1/2
R2 s1/3 - R3 s1/3
R3 s1/1 - R5 s1/1
Anyway have a look at the sh run .
10-19-2008 07:52 AM
R4(config-if)#do sh run
Building configuration...
Current configuration : 1059 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R4
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
memory-size iomem 5
!
!
ip cef
!
!
ip multicast-routing
!
!
!
!
interface Loopback0
ip address 5.5.5.5 255.255.255.0
!
interface FastEthernet0/0
no ip address
shutdown
duplex auto
speed auto
!
interface Serial1/0
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/1
ip address 24.0.0.2 255.255.255.252
ip pim sparse-dense-mode
serial restart-delay 0
clock rate 64000
!
interface Serial1/2
ip address 45.0.0.1 255.255.255.252
ip pim sparse-dense-mode
serial restart-delay 0
clock rate 64000
!
interface Serial1/3
no ip address
shutdown
serial restart-delay 0
!
router ospf 1
log-adjacency-changes
network 5.5.5.5 0.0.0.0 area 1
network 24.0.0.2 0.0.0.0 area 1
network 45.0.0.1 0.0.0.0 area 1
!
ip http server
!
control-plane
!
!
!
!
line con 0
line aux 0
line vty 0 4
login
!
!
end
R2#sh run
Building configuration...
Current configuration : 1236 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R2
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
memory-size iomem 5
!
!
ip cef
!
!
ip multicast-routing
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
interface Loopback0
ip address 1.1.1.1 255.255.255.0
!
interface Loopback1
ip address 3.3.3.3 255.255.255.0
!
interface FastEthernet0/0
no ip address
shutdown
duplex auto
speed auto
!
interface Serial1/0
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/1
ip address 12.0.0.2 255.255.255.252
ip pim sparse-dense-mode
serial restart-delay 0
clock rate 64000
!
interface Serial1/2
ip address 24.0.0.1 255.255.255.252
ip pim sparse-dense-mode
serial restart-delay 0
clock rate 64000
!
interface Serial1/3
ip address 23.0.0.1 255.255.255.252
ip pim sparse-dense-mode
serial restart-delay 0
clock rate 64000
!
router ospf 1
log-adjacency-changes
network 1.1.1.1 0.0.0.0 area 1
network 3.3.3.3 0.0.0.0 area 1
network 12.0.0.2 0.0.0.0 area 1
network 23.0.0.1 0.0.0.0 area 1
network 24.0.0.1 0.0.0.0 area 1
!
ip http server
!
!
!
!
!
!
control-plane
!
!
!
!
!
!
!
!
!
line con 0
line aux 0
line vty 0 4
login
!
!
end
10-19-2008 07:53 AM
R3#sh run
Building configuration...
Current configuration : 1306 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R3
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
memory-size iomem 5
!
!
ip cef
!
!
ip multicast-routing
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
interface Loopback0
ip address 2.2.2.2 255.255.255.0
ip pim sparse-dense-mode
!
interface Loopback1
ip address 4.4.4.4 255.255.255.0
!
interface FastEthernet0/0
no ip address
shutdown
duplex auto
speed auto
!
interface Serial1/0
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/1
ip address 35.0.0.1 255.255.255.252
ip pim sparse-dense-mode
serial restart-delay 0
clock rate 64000
!
interface Serial1/2
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/3
ip address 23.0.0.2 255.255.255.252
ip pim sparse-dense-mode
serial restart-delay 0
clock rate 64000
!
router ospf 1
log-adjacency-changes
network 2.2.2.2 0.0.0.0 area 1
network 4.4.4.4 0.0.0.0 area 1
network 23.0.0.2 0.0.0.0 area 1
network 35.0.0.1 0.0.0.0 area 1
!
ip http server
!
!
ip pim send-rp-announce Loopback0 scope 10 group-list 10
ip pim send-rp-discovery Loopback0 scope 10
!
access-list 10 permit 226.0.0.1
!
!
!
control-plane
!
!
!
!
!
!
!
!
!
line con 0
line aux 0
line vty 0 4
login
!
!
end
R5#sh run
Building configuration...
Current configuration : 1175 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R5
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
memory-size iomem 5
!
!
ip cef
!
!
ip multicast-routing
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
interface Loopback0
ip address 6.6.6.6 255.255.255.0
ip igmp join-group 226.0.0.1
!
interface Loopback1
ip address 7.7.7.7 255.255.255.0
ip igmp join-group 227.0.0.1
!
interface FastEthernet0/0
no ip address
shutdown
duplex auto
speed auto
!
interface Serial1/0
no ip address
shutdown
serial restart-delay 0
!
interface Serial1/1
ip address 35.0.0.2 255.255.255.252
ip pim sparse-dense-mode
serial restart-delay 0
clock rate 64000
!
interface Serial1/2
ip address 45.0.0.2 255.255.255.252
ip pim sparse-dense-mode
serial restart-delay 0
clock rate 64000
!
interface Serial1/3
no ip address
shutdown
serial restart-delay 0
!
router ospf 1
log-adjacency-changes
network 6.6.6.6 0.0.0.0 area 1
network 35.0.0.2 0.0.0.0 area 1
network 45.0.0.2 0.0.0.0 area 1
!
ip http server
!
!
!
!
!
!
control-plane
!
!
!
!
!
!
!
!
!
line con 0
line aux 0
line vty 0 4
login
!
!
end
10-19-2008 07:58 AM
Also kindly let me know how u would use "ip policy route-map" in this case to influence 6.6.6.6 path through 24.0.0.1 on R4 just to check to see if i made a mistake.
Thanks,
Ryel
10-19-2008 12:28 PM
Hello Ryel,
your topology with default settings is a symmetric square.
two notes are important here :
a)
packets locally generated by the router can be redirected only by applying the route-map in global config mode:
ip local policy route-map
there's no external input interface for locally generated traffic so this command is needed.
b)
The effect is local to the node:
if you have to build a multi-hop alternate path you need to configure PBR on all nodes on the path
even if R4 uses the command described above the result could be different then expected:
from the point of view of R2 net 6.6.6.6/32 is reachable via two equal cost paths:
one via R3 and one via R4 itself !
so you need :
on R4 the route-map applied with ip local policy that will send the packets out R4:s1/1 (set interface s1/1)
on R2 a route-map defined in the same way applied on s1/2 with action set interface s1/3 to R3.
Once packets are sent to R3 it will forward them to R5 on their direct link.
Hope to help
Giuseppe
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide