will the computes ping or not

kingshere

Hi all

I went for an interview and was asked a question in the below mentioned scenario.

Three routers (R1, R2, R3) all connected using Ethernet cables. All of routers have end devices connected to then. Will the end-devices ping each other in case all the three routers have the same routing table.

R1, R2 and R3

---

10.x.x.x was used on end-device 1
20.x.x.x was used on end-device 2
30.x.x.x was used on end-device 3

(in total 9 devices, 3 each on each router)

Interviewer said that networks of series 10.x.x.x, 20.x.x.x, 30.x.x.x are available on all three routers.
Routing protocol can be either RIP or EIGRP.

Now as far as my understanding goes they should ping as the routing table is updated with all the three routes. But then in case there is route summarization will they still ping?

Thanks
Kingshere

james43026

I think your interviewer either didn't know much about networking, or they were just throwing you a curveball. If the routers have routes to those networks, then they will be able to route ping's. Summary routes will not have an affect on routing packets between these networks unless the summary routes were entered incorrectly or are not neccessary. But in this case, there would be no need or summary routes. If you were to use summary routes with RIP in this network you could possibly run into routing loops, as EIGRP has better loop prevention mechanisms.

kingshere

hi, thanks for replying

In case EIGRP is used and route summarization is on, how will the routers decide where to forward the packet to, as all the routers will have the same summarized route.

Since all the routers have the same network table which is summarized.

Nans

kingshere wrote: »

hi, thanks for replying

In case EIGRP is used and route summarization is on, how will the routers decide where to forward the packet to, as all the routers will have the same summarized route.

Since all the routers have the same network table which is summarized.

Buddy the first point consultants say about summarizations is they must be entered manually and the auto summarization must be turned off or they will create loops if there are discontiguous networks. So i will say tell the interviewer that gong with the industrial best practices they must be able to ping each other.

satishtech

EIGRP has auto summarization enabled by default.

I am confused by the last question...

Nans

james43026 wrote: »

But in this case, there would be no need or summary routes. If you were to use summary routes with RIP in this network you could possibly run into routing loops, as EIGRP has better loop prevention mechanisms.

James correct em if I am wrong.

Even in EIGRP the routes are summarized and the router has no idea coz it is just summarizing and sending the addresses and since it is receives the same summary from many sides it discard the packet there or donno where to send it. May be there might be extra info in CCNP or CCIE studies but for CCNA thats what i studied.

Regards

Mow

I'm confused. It looks like you're saying that each router has an interface in each subnet, is that correct?

kingshere

hi all

So here is what i can make out of the discussion.

1. If the routes are manually summarized the computers will ping each other as then the routers will know which router has which route.
2. If the routes are auto summarized the computer might not ping.

Now as far as i remember the question i was asked that all the routers have the same summarized routes meaning 10.x.x.x 20.x.x.x 30.x.x.x on all 3 routers.

In this scenario if i ping End-Device on R3 from End-Device on R1 then how will the router R1 decide where to forward the packet ( should it be sent to R2 or R3 as both have the same summarized route).

And of the routes are summarized automatically it will have the same subnet mask too ( i brought this thing up as there was no subnet mask mentioned in the question)