Router – Loop redirect when ping the gateway

pingrouter

I have a router with WAN and LAN setup and act as DHCP server/gateway on my local LAN. The IP address is 192.168.1.1.

Today, I was hit by an internet failure and I checked the ping and get this weird ping result. Why the router continues to look for himself?

From 192.168.1.88: icmp_seq=6 Redirect Host(New nexthop: 192.168.1.1)
From 192.168.1.88: icmp_seq=6 Redirect Host(New nexthop: 192.168.1.1)
...........

Best Answer

ICMP Redirects are sent by a router when there is a more direct route from the client to the destination. This implies that your client is not actually using 192.168.1.1 as its default route, but rather is using 192.168.1.88 -- what does the routing table on the source look like?

Your setup is not very clear from your question though: which machine (and IP) are you pinging from, what IP are you pinging, and what is the network path between the source and the destination (routers, switches, APs, virtual machine hosts, etc.).

Related Solutions

Ping a Specific Port

You can't ping ports, as Ping is using ICMP which is an internet layer protocol that doesn't have ports. Ports belong to the transport layer protocols like TCP and UDP.

However, you could use nmap to see whether ports are open or not

nmap -p 80 example.com

Edit: As flokra mentioned, nmap is more than just a ping-for-ports-thingy. It's the security auditers and hackers best friend and comes with tons of cool options. Check the doc for all possible flags.

Windows – Ping only works after about 30 seconds

This can sometimes happen if a ping is crossing a network security device. In some cases, pinging by DNS name will trigger a URL filter in a UTM device. It may take several seconds to get a positive or negative response which cases a delay in ICMP. Once a positive response has been received, then future pings are allowed until a timer expires. That logic depends on how the security policy is set up.

So why would segment 2 be affected and not segment 1? In this theory, it's a rather simple matter of different policies for different segments. Perhaps there is an intentional difference in some kind of security context that is having unintended consequences.

Troubleshooting steps:

Ping LAN 2 from your gateway device itself. See if you can ping from the device using a Segment 2 context.
Capture traffic from both the pinger and pingee, then compare dumps. See how long of a delay there is between when the pinger sends and the pingee receives. If it's mere milliseconds, then there's something wrong with the return trip. If it's 30 seconds, then some device in between is holding the traffic.

Best Answer

Related Solutions

Ping a Specific Port

Windows – Ping only works after about 30 seconds

Troubleshooting steps:

Related Topic