A journey with my kiss’x'

Cisco policy based nat multihoming isp without bgp

June 14th, 2009 Benny Prasetio

cisco policy based nat multihoming isp without bgp

If you have 2 connection, how configure to adopt multi link failover ? Here I give the example how to configure it on Cisco 1841 Router.

This configuration topology here consists of two vlan users :
1. VLAN Bos 192.168.0.0/24 primarily connect to ISP A but when connection to ISP A is lost the traffic will be reroute through ISP B.
2. VLAN Staff, daily connection is through ISP B and never going through ISP A.

Because the users VLAN is behind of ASA firewall, so the VLAN Bos will be translated using outside interface of firewall, and VLAN Staff will be translated to 172.16.100.5
Here I am not explain how is the configuration of firewall, insted of focusing on how routing on the router works.
Here is the configuration :

*********************************
track 123 ip sla 1 reachability
!
track 124 ip sla 2 reachability
!
interface FastEthernet0/0
ip address 202.1.2.2 255.255.255.240
ip nat outside
ip virtual-reassembly
duplex auto
speed auto
!
interface FastEthernet0/1
ip address 192.168.2.1 255.255.255.0
ip nat outside
ip virtual-reassembly
duplex auto
speed auto
!
interface FastEthernet0/1/0
ip address 172.16.100.2 255.255.255.0
ip nat inside
ip virtual-reassembly
ip policy route-map dual-isp
duplex auto
speed auto
!
ip route 0.0.0.0 0.0.0.0 202.1.2.1
!
ip nat inside source list adsluser interface FastEthernet0/1 overload
ip nat inside source route-map policy-based-nat interface FastEthernet0/0 overload
ip nat inside source route-map policy-based-nat2 interface FastEthernet0/1 overload
!
access-list extended Dedicated_Internet_user
permit ip host 172.16.100.1 any
ip access-list extended adsluser
permit ip host 172.16.100.5 any
!
ip sla 1
icmp-echo 202.1.2.1source-ip 202.1.2.2
ip sla schedule 1 life forever start-time now
ip sla 2
icmp-echo 192.168.2.99
ip sla schedule 2 life forever start-time now
route-map policy-based-nat permit 10
match ip address Dedicated_Internet_user
match interface FastEthernet0/0
!
route-map policy-based-nat2 permit 10
match ip address Dedicated_Internet_user
set ip next-hop interface FastEthernet0/1
!
route-map dual-isp permit 10
match ip address Dedicated_Internet_user
set ip next-hop verify-availability 202.1.2.1 10 track 123
set ip next-hop verify-availability 192.168.2.99 20 track 124
!
route-map dual-isp permit 20
match ip address adsluser
set ip default next-hop 192.168.2.99
!

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Cisco EIGRP variance load balancing

May 2nd, 2009 Benny Prasetio
cisco eigrp variance load balancing

Cisco EIGRP variance load balancing

This is my first blog for not writing about photo of food and travelling, this CCIE blog actually dedicated for who want to learn CCIE and special mnemonic purpose for me.

This explanation here may not very detail because i’m talk about concept only, you still should find from Cisco Doc for further explanation. How Cisco EIGRP over equal or not equal cost works ?

Equal-cost load balancing is the ability of a router to distribute traffic over all  its network ports that are the same metric from the destination address. Cisco IOS software by default will install up to four equal-cost paths in the routing table for most routing protocols

COMMAND : router(config-router)# variance multiplier

a value from 1 to 128, used for load balancing. The default is 1, which  indicates equal-cost load balancing. The multiplier defines the range of metric  value that are accepted for load balancing by eigrp process.

Load balancing can use only feasible paths, and the routing table includes only  these paths.

From Router 1 perspective to reach Network X :
B, D, and F is an administrative distance
A+B, C+D. and E+F is feasible distance
Through router C is best router so current FD is C+D

Load balancing can use only feasible paths.

2 feasibility condition are :
- The current FD (is the smallest FD) is C+D must be greater than AD  learned from the other router (in this case is Router 2). This is to prevent loops.
- The variance multiplied by the current FD [ 2 x (C+D) ] must greater than  the metric through alternative FD is (A+B).
note : Router 4 never considered to load balance whatever variance value, because F > C+D

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