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Beginner

Cant ping across Router on a Stick

I made a network and implemented VLANs and everything is working except that i cannot ping past the gateway of the router on a stick from the VLANs. Everything in the VLAN network can communicate fine and also receives DHCP from outside the VLAN network using an IP helper address.. Everything outside the VLAN network can communicate fine as well. When I try to ping from a PC on a VLAN the ARP request times out.

 

This is what the packet shows before it times out.

1. The next-hop IP address is a unicast. The ARP process looks it up in the ARP table.

2. The next-hop IP address is not in the ARP table. The ARP process tries to send an ARP request for that IP address and buffers this packet.

 

This is the same PC successfully pinging the gateway.

C:\>ping 172.16.0.254

 

Pinging 172.16.0.254 with 32 bytes of data:

 

Reply from 172.16.0.254: bytes=32 time<1ms TTL=255

Reply from 172.16.0.254: bytes=32 time=1ms TTL=255

Reply from 172.16.0.254: bytes=32 time<1ms TTL=255

Reply from 172.16.0.254: bytes=32 time<1ms TTL=255

 

Ping statistics for 172.16.0.254:

Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),

Approximate round trip times in milli-seconds:

Minimum = 0ms, Maximum = 1ms, Average = 0ms

 

This is the same PC pinging the other interface on the router.

C:\>ping 172.16.4.230

 

Pinging 172.16.4.230 with 32 bytes of data:

 

Request timed out.

Request timed out.

Request timed out.

Request timed out.

 

Ping statistics for 172.16.4.230:

Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

 

I attached a screenshot of what I set up. The large network on the right is the network with VLANs and the colored circles are the different VLANs. I am trying to ping from PC24 on the left most Red VLAN to Router 2which is the router on a stick. I am learning networking and have set up these labs for practice so if you notice anything that I need to improve on please let me know. Thank you.

Everyone's tags (4)
1 ACCEPTED SOLUTION

Accepted Solutions
VIP Advisor

Re: Cant ping across Router on a Stick

Hi there,

You say PC24 is trying to ARP the IP address in another subnet (172.16.4.230)?  In this scenario it should be ARP'ing for its default gateway.

 

Can you confirm that the netmask and gateway is correctly set for PC24.

 

cheers,

Seb.

10 REPLIES 10
VIP Advisor

Re: Cant ping across Router on a Stick

Hi there,

You say PC24 is trying to ARP the IP address in another subnet (172.16.4.230)?  In this scenario it should be ARP'ing for its default gateway.

 

Can you confirm that the netmask and gateway is correctly set for PC24.

 

cheers,

Seb.

Beginner

Re: Cant ping across Router on a Stick

I checked the default gateway that the machine received from the DHCP server and it was not correct. I then checked the DHCP server to verify that the configuration was correct and they were. What I forgot about was the old DHCP settings for this subnet before i created VLANs. The hosts in what was subnet A was receiving data from the original pool instead of the new VLAN pool. I deleted the original configuration for that pool and did 'ipconfig /release' and 'ipconfig /renew' on the hosts and they all retrieved the correct configurations from the DHCP server and everything is working correctly. Thank you very much.

 

This was such a simple mistake that I should checked first. For future reference what made you go first to the gateway on the hosts? I knew there was an issue with the gateway I just overlooked the old DHCP pool.

Advocate

Re: Cant ping across Router on a Stick

Hi @Jon Stinnett ,

 

Connectivity problems may be due to several reasons, so I suggest you attach the exercise to make the necessary revisions.
To be able to attach the exercise, first you must compress it using winzip, winrar, etc.

 

Regards

Beginner

Re: Cant ping across Router on a Stick

I attached the excercise. After looking for information that another person asked regarding my issue I found that I forgot about the the old DHCP settings for this subnet before I created VLANs. The hosts in what was subnet A was receiving data from the original pool instead of the new VLAN pool. I deleted the original configuration for that pool and did 'ipconfig /release' and 'ipconfig /renew' on the hosts and they all retrieved the correct configurations from the DHCP server and everything is working correctly.

 

Thank you for your quick response. Like I mentioned, I am learning networking and I am setting up these excersises to give me practice and a challenge. If you have any tip or ideas to help me with this excercise I will really appreciate it. I continue to build of finished exercises with new goals and this one I am trying to focus on VLANs, PVST+, maybe VTP, and Router on a Stick. Next I want to learn and implement network security.

Advocate

Re: Cant ping across Router on a Stick

Hi @Jon Stinnett ,

 

I attached your exercise but with a challenge.
To do this, you should look for other concepts that will help you to reinforce your knowledge of networks.
If you were a student in my institution, this knowledge would correspond to the CCNA 2 and 3 courses.

 

What you should look for and configure is specified within the exercise.
If something is not indicated, you are free to choose the best option to achieve the objective.

 

Regards

Beginner

Re: Cant ping across Router on a Stick

Thank you for the challenge and helping me learn and practice. I attached the completed exercise.

Advocate

Re: Cant ping across Router on a Stick

Hi @Jon Stinnett,

 

I only found one detail.
In the border router you configured the same protocol (EIGRP) that the ISP had.
In real life this does not happen as it is a danger that from an external network know your networks, and no ISP would allow a user to know theirs.

 

I made these changes to solve this:
-Eliminate the EIGRP protocol of the border router.
-In that router configure a default route, leaving the output interface that goes to the ISP (serial2 / 0)
-Propagate that route by default through the internal protocol (OSPF).
-Eliminate the redistribution in OSPF, since EIGRP ceased to exist.

 

I enclose the exercise with the mentioned changes.

 

I really congratulate you for the achievement, since you advanced a lot in this first attempt.
I encourage you to continue with this procedure.

 

Regards

Beginner

Re: Cant ping across Router on a Stick

Thats great, thank you very much.

VIP Advisor

Re: Cant ping across Router on a Stick

Hello

That network is quite  convoluted considering your are running nat-on-stick , you have multiple routers and dont identify whchc router is performing the inter-vlan routing.

 

Can you elaborate on the topology please , Also this looks like a packer tracer simulation so maybe also attach the PT file for this network.



kind regards
Paul

Please rate and mark posts accordingly if you have found any of the information provided useful.
It will hopefully assist others with similar issues in the future
Beginner

Re: Cant ping across Router on a Stick

Router 2 is the Router on a Stick and all the switches on the right connected to it are the VLANs. I was able to find the issue which was that the gateway on the hosts was wrong. The gateway was from the old DHCP pool for this subnet prior to implementing VLANs. I deleted the old DHCP server pool and did 'ipconfig /release' and 'ipconfig /renew' on the hosts and everything started working properly.

 

I attached the excercise to this response anywaye if you want to critique it. I am learning networking and I am setting up these excersises to give me practice and a challenge. If you have any tip or ideas to help me with this excercise I will really appreciate it. I continue to build of finished exercises with new goals and this one I am trying to focus on VLANs, PVST+, maybe VTP, and Router on a Stick. Next I want to learn and implement network security.

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