In this
article, I will explain how we can configure Cisco routers for WAN redundancy
and automatic change routing using IP SLA (Service level agreement).
IP SLA
is a feature that enable the network administrators to analyze ip service
levels for ip applications and services, and understand the network
performance. It measures some parameters such as delay, jitter, packet loss,
path, connectivity and other parameters, thus creating accurate statistics and
depending on these measurements or statistics, the routers can take an action
as we will see in this article.
In our
Scenario, we have branch site connected to the main site using two links, one
of them will be used as primary link that will carry all the data from the
branch to the main site, and backup link (Secondary link) that will be used if
the primary link goes down. in this article we will be covering just the
icmp-echo feature used by IP SLA.
The idea
of this lab is configuring two routes on the branch router R3 to get the the
main site -destination network 192.168.40.0/24, and using SLA icmp-echo feature
to send icmp-echo to R1. if R3 didn't receive reply from R1, R3 will consider
it down and automatically uses the other route or link to reach the main site
network.
Configuration
Steps
1-Conguring
IP SLA to ping a target : the target is R1 in the main site that has ip
192.168.20.2.This ping that shown in the image below will be sent every 10
second using frequency 10 command. R3 will consider R1 down if it didn't
receive reply from it within 6 seconds using timeout 6000 command. It is
possible schedule the SLA operation in different ways but in this article I
want to start the ip SLA operation immediately and forever.
2-Track
the state of the IP SLA Reachability: the “track state” will be down only in
case of a ICMP timeout using track 1 ip sla 1 reachability command.
By using the above command, we define an object that tracks the SLA probe (track object number is 10 in this example). This can be accomplished by using the IOS Track Object as shown above. The above command will track the state of the IP SLA operation. If there are no ping responses from the next-hop IP -defined in sla 1- the track will go down and it will come up when the ip sla operation starts receiving ping response.
By using the above command, we define an object that tracks the SLA probe (track object number is 10 in this example). This can be accomplished by using the IOS Track Object as shown above. The above command will track the state of the IP SLA operation. If there are no ping responses from the next-hop IP -defined in sla 1- the track will go down and it will come up when the ip sla operation starts receiving ping response.
To show
the state of the Reachability use sh track command.
3- Define the tracked route : add the track statement to the route pointing to R1 , The track number specifies that the static route will be installed only if the state of the configured track object is up. Hence if the track status is down the secondary route will be used to forward all the traffic.
3- Define the tracked route : add the track statement to the route pointing to R1 , The track number specifies that the static route will be installed only if the state of the configured track object is up. Hence if the track status is down the secondary route will be used to forward all the traffic.
4-
verify your configuration : The commands in the image below are issued after
making sure that all the links (primary and secondary is up) between the branch
and the main site. The image below shows that R3 can ping to R1, the track
state is up as shown in the show track command,
and the router uses R1 IP address 192.168.20.2 as a next hop to reach
the main site destination network 192.168.40.0/24.
Now , i
removed the link between R3 and R1, Let's see what happened in R3. As you see
in the image below, R3 changes the route automatically to R2 ip address
192.168.30.2.
More
explanation about the configuration, watch the video at top of this article or
visit the following links
To
download the configuration file, click on the following link
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Dear Bro ,
ReplyDeleteI try to follow your this topology..but now , i'm facing some problem.
I cannot type the command as ( track 10 ip sla 1 rechability ) in config mode.
My router is 3725. could u pleased suggest me?
which router software image did you run on this video. Can you please share the image?
ReplyDeleteThis is the image: http://adf.ly/1TXSSz
DeleteThis comment has been removed by the author.
ReplyDeleteIs there a way to have Load Balancing (Active-Active) and Failover (Active-Standby) at the same time on Router cisco? Your test is Active-Standby, am I right?
ReplyDeleteI HAVE CISCO 1900 ROUTER,I CAN NOT TYPE COMMAND ip sla 1 in config mode
ReplyDeleteuse: track 10 rtr 1 reachability command, this command performs the same purpose of track 10 ip sla 1 rechability in the older cisco ios releases.
Deletewith Cisco IOS Release 12.4(20)T, 12.2(33)SXI1, 12.2(33)SRE and Cisco IOS XERelease 2.4, the track rtr command is replaced by the track ip sla command.
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ReplyDeletegreat
ReplyDelete