Offset-list and Distance command Revealed

Offset-list and Distance command Revealed

Offset-list and distance command revealedOffset-list basically used for altering the route metric. I have given an example to alter a route metric with the help of offset-list.

We are running EIGRP protocol in all the above routers and advertising all the associated networks.

So in the above task, we need to change the metric of a route (70.0.0.0/24) coming from R3 to R2 so what will be the commands.
On R2:-# offset-list 1 in 170 s1/0# access-list 1 permit 70.0.0.0 0.0.0.255

Now if you see the routing table of R2, you can see the metric of route(70.0.0.0/24) changed to a value of 170.Offset-list can also be used to discard a route from routing table. We are using the same diagram mentioned above but the protocol running is RIP and we are advertising all the subnets in RIP. Below mentioned are the commands.On R2:-# offset-list 1 in 15 s1/0# access-list 1 permit 70.0.0.0 0.0.0.255As you know the 15 metric is unreachable for RIP so the route will not be entered in R2 routing table and hence not reached to R1.Offset-list can also be used in out direction and workings will the same. Metric will be changed in the next hop router.Distance command basically used for manipulating the AD of routes. Below mentioned is the task.Refer the above mentioned diagram.We are running EIGRP in all the routers and all subnets are advertised in EIGRP. Now we want to change the AD of 70.0.0.0/24 route to 199.On R2# distance 199 20.0.0.2 0.0.0.0 1# access-list 1 permit 70.0.0.0 0.0.0.255Above two commands states that routes coming from 20.0.0.2 address and matching the access-list 1, AD should be changed to 199. You can see the changed AD by verifying the routing table of R2.You can also change the AD of all internal and external routes of EIGRP# distance Eigrp 99 200Command mentioned above states that change the AD for all internal routes to 99 and changed the AD for all external routes to 199. You can validate by verifying the routing table of R2.Distance command also can be used to filter routes. As the AD of 255 is considered as unreachable so we will modify the AD for 70.0.0.0/24 route to 255 and route will not be installed in R2 routing table.On R2:-# distance 255 20.0.0.2 0.0.0.0 1# access-list 1 permit 70.0.0.0 0.0.0.255Now after running this command in R2, 70.0.0.0/24 route will be out of R2 routing table and you can validate it by verifying the routing table of R2.Please let me know, if you find the post useful.RegardsMahirawatmohinder@yahoo.co.in

How to reset root password in Suse Linux

Hi All,
I was installing VM for suse linux in my system for GNS3 system and i faced the problem of breaking root password in Susue linux.
Process
---------
1.) Boot in suse linux and type in boot options
"init=/bin/bash" for grub bootloader
"linux init=/bin/bash" for LILO bootloader

2,) Type mount and check if you have rw permissions.
3.) if it is not mounted in rw remount it as per below command
mount -o remount, rw/
4.) type password
and chnage the password
5.) reboot
reboot the system
Bingo !! your root password has been changed.

OSPF Default route Injection

Hi All,

Recently I was working on our new data center implementation and I came across OSPF default route injection mechanism. Please refer the topology showed on the right.

I was suppose to generate a default route from WAN routers to inside the network up to the edge router. We were not getting any default route from AT&T (FYI).

Think of possible options before reading through solutions.

If I configure (default-information originate) on both WAN routers, it will not generate the default route inside as this command do not generate default route by its own. it needs a default route in routing table of WAN routers before it inject a default route in OSPF.

The other option, we were having to configure(default-information originate always) on both WAN routers and both WAN routers will inject default route in topology but in case of any WAN link down, it will add a extra hop in traffic flow. For ex:- If WAN link 1 goes down but still WAN1 router will be injecting default route in topology so the traffic reach to WAN1 router destined for outside need to travel to WAN2 router to reach outside world which is not an optimal solution.

I configured a floating static route in both WAN routers pointing to AT&T side routers interface IP address.

Like 0.0.0.0 0.0.0.0 10.0.0.2 (AT&T side WAN router interface IP is 10.0.0.2)

Now WAN1 and WAN2 both routers have default route in thier routing table. I configured default-information originate in both WAN routers. This time OSPF will inject a route inside as we have a default route in WAN routers. Bingo !!

if any wan link go down, default floating route will be removed from routing table and that WAN router will stop injecting default route inside.

There is one more way with conditional route advertisement. I will explain it in next post.

Till then...Keep Routing..