DM-VPN - EIGRP route influence - Part II

following the lab from my previous post -MPLS-VPN and Dual DM-VPN networks - Part I

(http://www.madari.co.il/2014/10/step-by-step-mpls-vpn-and-dual-dm-vpn.html) now we have fully operational network and i need to do some traffic manipulations from the branches to the data center.

Now the customer network is built from two layers:

Layer-1 – Configured using BGP over the SP network and advertise the loopback interfaces only as an infrastructure to the DM-VPN.

Layer-2 – Customer network which runs over the DM-VPN network using EIGRP as routing protocol.

In the following tasks I will show the necessary steps to change the topology to redundant active/active deterministic topology.

Task 1: Dual link branch configuration

All branch routers which have dual uplinks to the SP network will utilize both links, one for each tunnel.

In order to accomplish this we will use 2 loopbacks and inbound and outbound route-maps on BGP peer advertisement.

R9 outbound policy:

interface Loopback91  ip address 9.9.9.1 255.255.255.255 ! interface Loopback92  ip address 9.9.9.2 255.255.255.255 ! ip prefix-list PL_LO91 seq 5 permit 9.9.9.1/32 ! ip prefix-list PL_LO92 seq 5 permit 9.9.9.2/32 ! route-map RM_BGP_R7_OUTBOUND permit 10  match ip address prefix-list PL_LO92  set as-path prepend 65009 65009 65009 ! route-map RM_BGP_R7_OUTBOUND permit 999 ! route-map RM_BGP_R8_OUTBOUND permit 10  match ip address prefix-list PL_LO91  set as-path prepend 65009 65009 65009 ! route-map RM_BGP_R8_OUTBOUND permit 999

This will assure inbound traffic from the SP network to R9 loopback 91 through R7 and R9 loopback 92 through R8.

R4#sh ip route vrf ABC 9.9.9.1 Routing Table: ABC Routing entry for 9.9.9.1/32   Known via "bgp 65006", distance 200, metric 0   Tag 65009, type internal   Last update from 7.7.7.7 00:14:08 ago   Routing Descriptor Blocks:   * 7.7.7.7 (default), from 6.6.6.6, 00:14:08 ago       Route metric is 0, traffic share count is 1       AS Hops 1       Route tag 65009       MPLS label: 26       MPLS Flags: MPLS Required R4#sh ip route vrf ABC 9.9.9.2 Routing Table: ABC Routing entry for 9.9.9.2/32   Known via "bgp 65006", distance 200, metric 0   Tag 65009, type internal   Last update from 8.8.8.8 00:13:40 ago   Routing Descriptor Blocks:   * 8.8.8.8 (default), from 6.6.6.6, 00:13:40 ago       Route metric is 0, traffic share count is 1       AS Hops 1       Route tag 65009       MPLS label: 27       MPLS Flags: MPLS Required R4#

Now let’s change R9 outbound traffic:

ip prefix-list PL_NET_LO1 seq 5 permit 1.1.1.1/32 ! ip prefix-list PL_NET_LO2 seq 5 permit 2.2.2.2/32 ! route-map RM_R8_INBOUND permit 10  match ip address prefix-list PL_NET_LO2  set weight 1500 ! route-map RM_R8_INBOUND permit 999 ! route-map RM_R7_INBOUND permit 10  match ip address prefix-list PL_NET_LO1  set weight 1500 ! route-map RM_R7_INBOUND permit 999 ! router bgp 65009  neighbor 10.1.79.7 route-map RM_R7_INBOUND in  neighbor 10.1.89.8 route-map RM_R8_INBOUND in

Again this will assure outgoing traffic from R9 to R1 through R7 and R9 to R2 though R8.

R9#  show ip route 1.1.1.1 Routing entry for 1.1.1.1/32   Known via "bgp 65009", distance 20, metric 0   Tag 65006, type external   Last update from 10.1.79.7 00:13:47 ago   Routing Descriptor Blocks:   * 10.1.79.7, from 10.1.79.7, 00:13:47 ago       Route metric is 0, traffic share count is 1       AS Hops 2       Route tag 65006       MPLS label: none R9#  show ip route 2.2.2.2 Routing entry for 2.2.2.2/32   Known via "bgp 65009", distance 20, metric 0   Tag 65006, type external   Last update from 10.1.89.8 00:00:03 ago   Routing Descriptor Blocks:   * 10.1.89.8, from 10.1.89.8, 00:00:03 ago       Route metric is 0, traffic share count is 1       AS Hops 2       Route tag 65006       MPLS label: none

Now let’s advertise Lo91 and Lo92 through BGP and change the tunnel source interface accordingly on R9:

router bgp 65009  bgp log-neighbor-changes  network 9.9.9.1 mask 255.255.255.255  network 9.9.9.2 mask 255.255.255.255 ! interface Tunnel1  tunnel source Loopback91 ! interface Tunnel2  tunnel source Loopback92

Now all the traffic on tunnel 1, from/to R1, is going through R9-R7 link and all traffic on tunnel 2, from/to R2, goes through R9-R8 link - both directions!

Note that this has no influence on the upper layer network (customer networks) between the branch and the center which runs EIGRP over DM-VPN on the tunnels.

Task 2: EIGRP traffic influence from branch to center

In the current situation all branch routers learn data center networks (192.168.31-33.0/24) through both tunnels hence we have ECMP from the branch to the data center and the traffic is load-balanced.

R9:

R9#show ip route 192.168.31.0 Routing entry for 192.168.31.0/24   Known via "eigrp 1", distance 90, metric 27010560, type internal   Redistributing via eigrp 1   Last update from 172.2.0.2 on Tunnel2, 00:01:57 ago   Routing Descriptor Blocks:   * 172.2.0.2, from 172.2.0.2, 00:01:57 ago, via Tunnel2       Route metric is 27010560, traffic share count is 1       Total delay is 55100 microseconds, minimum bandwidth is 100 Kbit       Reliability 255/255, minimum MTU 1420 bytes       Loading 1/255, Hops 2     172.1.0.1, from 172.1.0.1, 00:01:57 ago, via Tunnel1       Route metric is 27010560, traffic share count is 1       Total delay is 55100 microseconds, minimum bandwidth is 100 Kbit       Reliability 255/255, minimum MTU 1420 bytes       Loading 2/255, Hops 2 R9#show ip route 192.168.32.0 Routing entry for 192.168.32.0/24   Known via "eigrp 1", distance 90, metric 26882560, type internal   Redistributing via eigrp 1   Last update from 172.1.0.1 on Tunnel1, 00:00:47 ago   Routing Descriptor Blocks:   * 172.1.0.1, from 172.1.0.1, 00:00:47 ago, via Tunnel1       Route metric is 26882560, traffic share count is 1       Total delay is 50100 microseconds, minimum bandwidth is 100 Kbit       Reliability 255/255, minimum MTU 1420 bytes       Loading 2/255, Hops 1     172.1.0.2, from 172.1.0.2, 00:03:50 ago, via Tunnel2       Route metric is 27010560, traffic share count is 1       Total delay is 55100 microseconds, minimum bandwidth is 100 Kbit       Reliability 255/255, minimum MTU 1420 bytes       Loading 1/255, Hops 2 R9#show ip route 192.168.33.0 Routing entry for 192.168.33.0/24   Known via "eigrp 1", distance 90, metric 27010560, type internal   Redistributing via eigrp 1   Last update from 172.2.0.2 on Tunnel2, 00:03:50 ago   Routing Descriptor Blocks:   * 172.2.0.2, from 172.2.0.2, 00:03:50 ago, via Tunnel2       Route metric is 27010560, traffic share count is 1       Total delay is 55100 microseconds, minimum bandwidth is 100 Kbit       Reliability 255/255, minimum MTU 1420 bytes       Loading 1/255, Hops 2     172.1.0.1, from 172.1.0.1, 00:03:50 ago, via Tunnel1       Route metric is 27010560, traffic share count is 1       Total delay is 55100 microseconds, minimum bandwidth is 100 Kbit       Reliability 255/255, minimum MTU 1420 bytes       Loading 1/255, Hops 2

There are several ways to influence EIGRP traffic and I will focus on two of them: route-map and offset list.

According to Marko Milivojevic post on Cisco support forums (URL: https://learningnetwork.cisco.com/thread/26400) as far as I understand we can’t change the metric of an EIGRP internal route using route-map and set metric command.

My tests on this lab shows slightly different, on the current configuration I see that both R1 and R2 are advertising network 192.168.31.0/24 as follow:

R1 EIGRP update pcap:

R2 EIGRP update pcap: 

You can see the wide metric setting for bandwidth which set to 100000.

Now I have configured the following on R1:

ip prefix-list PL_NET31 seq 5 permit 192.168.31.0/24 ! route-map RM_EIGRP_OUT permit 10  match ip address prefix-list PL_NET31  set metric 1000 10 255 1 1500 ! route-map RM_EIGRP_OUT permit 999 ! router eigrp 1  distribute-list route-map RM_EIGRP_OUT out Tunnel1

Now R1 is advertising network 192.168.31.0/24 with wide metric bandwidth of 100,

R1 EIGRP update pcap:

And we can see that R9 has now only one preferred path to network 192.168.31.0/24:

R9#    show ip route 192.168.31.0 Routing entry for 192.168.31.0/24   Known via "eigrp 1", distance 90, metric 26882560, type internal   Redistributing via eigrp 1   Last update from 172.1.0.1 on Tunnel1, 00:16:04 ago   Routing Descriptor Blocks:   * 172.1.0.1, from 172.1.0.1, 00:16:04 ago, via Tunnel1       Route metric is 26882560, traffic share count is 1       Total delay is 50100 microseconds, minimum bandwidth is 100 Kbit       Reliability 255/255, minimum MTU 1420 bytes       Loading 1/255, Hops 1

While all other networks are still multi-path equal cost:

R9#    show ip route 192.168.32.0 Routing entry for 192.168.32.0/24   Known via "eigrp 1", distance 90, metric 27010560, type internal   Redistributing via eigrp 1   Last update from 172.2.0.2 on Tunnel2, 00:18:20 ago   Routing Descriptor Blocks:   * 172.2.0.2, from 172.2.0.2, 00:18:20 ago, via Tunnel2       Route metric is 27010560, traffic share count is 1       Total delay is 55100 microseconds, minimum bandwidth is 100 Kbit       Reliability 255/255, minimum MTU 1420 bytes       Loading 1/255, Hops 2     172.1.0.1, from 172.1.0.1, 00:18:21 ago, via Tunnel1       Route metric is 27010560, traffic share count is 1       Total delay is 55100 microseconds, minimum bandwidth is 100 Kbit       Reliability 255/255, minimum MTU 1420 bytes       Loading 1/255, Hops 2 R9#    show ip route 192.168.33.0 Routing entry for 192.168.33.0/24   Known via "eigrp 1", distance 90, metric 27010560, type internal   Redistributing via eigrp 1   Last update from 172.2.0.2 on Tunnel2, 00:25:33 ago   Routing Descriptor Blocks:   * 172.2.0.2, from 172.2.0.2, 00:25:33 ago, via Tunnel2       Route metric is 27010560, traffic share count is 1       Total delay is 55100 microseconds, minimum bandwidth is 100 Kbit       Reliability 255/255, minimum MTU 1420 bytes       Loading 1/255, Hops 2     172.1.0.1, from 172.1.0.1, 00:25:33 ago, via Tunnel1       Route metric is 27010560, traffic share count is 1       Total delay is 55100 microseconds, minimum bandwidth is 100 Kbit       Reliability 255/255, minimum MTU 1420 bytes       Loading 1/255, Hops 2

So what’s happen here actually??? Also note that I lowered the bandwidth for this network (metric 1000 10 255 1 1500) and it made the opposite result – it made this network more preferred!!! 

I think the reason for this behavior related to the fact that I changed the EIGRP bandwidth and not the bandwidth setting of a particular interface.

As you may recall EIGRP metric calculation is (Bandwidth + Delay) * 256 = composite metric.

But before we run our calculation we need to scale the interface bandwidth and delay using the following formulas:

Scaled Bandwidth = (10 in power of 7 / Interface bandwidth)

Scaled Delay = (Delay/10)

When we use set metric on the route-map it change the EIGRP bandwidth without scaling it and as a result lower is better!

As for offset list things are pretty much straight forward, here is the configuration of R1:

ip access-list standard 32  permit 192.168.32.0 0.0.0.255  deny   any ! router eigrp 1  offset-list 32 out 10000 Tunnel1

We configure an ACL to express the network which we want to make less preferable and we advertise it out with offset list which actually just add more delay

R1 PIC

And R9 route table:

R9#    show ip route 192.168.32.0 Routing entry for 192.168.32.0/24   Known via "eigrp 1", distance 90, metric 27010560, type internal   Redistributing via eigrp 1   Last update from 172.2.0.2 on Tunnel2, 00:01:32 ago   Routing Descriptor Blocks:   * 172.2.0.2, from 172.2.0.2, 00:01:32 ago, via Tunnel2       Route metric is 27010560, traffic share count is 1       Total delay is 55100 microseconds, minimum bandwidth is 100 Kbit       Reliability 255/255, minimum MTU 1420 bytes       Loading 1/255, Hops 2

No R1 for this network in the routing table!

Although it’s still exist the EIGRP topology table:

R9#sh ip eigrp topology 192.168.32.0 EIGRP-IPv4 Topology Entry for AS(1)/ID(192.168.93.1) for 192.168.32.0/24   State is Passive, Query origin flag is 1, 1 Successor(s), FD is 27010560   Descriptor Blocks:   172.2.0.2 (Tunnel2), from 172.2.0.2, Send flag is 0x0       Composite metric is (27010560/156160), route is Internal       Vector metric:         Minimum bandwidth is 100 Kbit         Total delay is 55100 microseconds         Reliability is 255/255         Load is 1/255         Minimum MTU is 1420         Hop count is 2         Originating router is 192.168.33.1   172.1.0.1 (Tunnel1), from 172.1.0.1, Send flag is 0x0       Composite metric is (27020544/166144), route is Internal       Vector metric:         Minimum bandwidth is 100 Kbit         Total delay is 55490 microseconds         Reliability is 255/255         Load is 1/255         Minimum MTU is 1420         Hop count is 2         Originating router is 192.168.33.1

Hence in case of failure of tunnel 2/ R2 we still have route to this network.

In order to continue this lab I used the route-maps method on both R1 and R2 for getting this final result:

R9#sh ip route 192.168.31.0 Routing entry for 192.168.31.0/24   Known via "eigrp 1", distance 90, metric 26882560, type internal   Redistributing via eigrp 1   Last update from 172.1.0.1 on Tunnel1, 00:00:09 ago   Routing Descriptor Blocks:   * 172.1.0.1, from 172.1.0.1, 00:00:09 ago, via Tunnel1       Route metric is 26882560, traffic share count is 1       Total delay is 50100 microseconds, minimum bandwidth is 100 Kbit       Reliability 255/255, minimum MTU 1420 bytes       Loading 1/255, Hops 1 R9#sh ip route 192.168.32.0 Routing entry for 192.168.32.0/24   Known via "eigrp 1", distance 90, metric 26882560, type internal   Redistributing via eigrp 1   Last update from 172.2.0.2 on Tunnel2, 00:00:02 ago   Routing Descriptor Blocks:   * 172.2.0.2, from 172.2.0.2, 00:00:02 ago, via Tunnel2       Route metric is 26882560, traffic share count is 1       Total delay is 50100 microseconds, minimum bandwidth is 100 Kbit       Reliability 255/255, minimum MTU 1420 bytes       Loading 1/255, Hops 1 R9#sh ip route 192.168.33.0 Routing entry for 192.168.33.0/24   Known via "eigrp 1", distance 90, metric 27010560, type internal   Redistributing via eigrp 1   Last update from 172.2.0.2 on Tunnel2, 00:50:30 ago   Routing Descriptor Blocks:   * 172.2.0.2, from 172.2.0.2, 00:50:30 ago, via Tunnel2       Route metric is 27010560, traffic share count is 1       Total delay is 55100 microseconds, minimum bandwidth is 100 Kbit       Reliability 255/255, minimum MTU 1420 bytes       Loading 1/255, Hops 2     172.1.0.1, from 172.1.0.1, 00:50:30 ago, via Tunnel1       Route metric is 27010560, traffic share count is 1       Total delay is 55100 microseconds, minimum bandwidth is 100 Kbit       Reliability 255/255, minimum MTU 1420 bytes       Loading 1/255, Hops 2

Network 192.168.31.0/24 through R1

Network 192.168.32.0/24 through R2

And network 192.168.33.0/24 through both R1 and R2.

Next post I will have to handle traffic from the center to the branches…

Bye!

References:

Manipulating EIGRP metrics with route maps post on Cisco Support Forums

https://learningnetwork.cisco.com/thread/26400

Enhanced Interior Gateway Routing Protocol (EIGRP) Wide Metrics

http://www.cisco.com/c/en/us/products/collateral/ios-nx-os-software/enhanced-interior-gateway-routing-protocol-eigrp/whitepaper_C11-720525.html