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I'm assigned to a public IP address from my organization. Here is my default route:

IP: 45.150.164.x

Gateway: 45.150.164.1

netmask: 255.255.255.0

And here is the result of traceroute 8.8.8.8 from my PC(45.150.164.x):

1 1 ms <1 ms <1 ms 192.168.250.250

2 2 ms <1 ms 1 ms 192.168.249.178

3 1 ms 1 ms 1 ms 192.168.249.201

......

You can see hop 1 is not the gateway 45.150.164.1. But the MAC address of 192.168.250.250 is same as 45.150.164.1's.(I made arp requests.)

Does the interface of 45.150.164.1 have two different IP addresses?

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  • Unfortunately, questions about networks you do not directly control are off-topic here.
    – Ron Maupin
    Feb 27, 2023 at 18:51

2 Answers 2

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Routers have multiple interfaces and subsequently multiple IP addresses.

While it is nice and transparent when they send ICMP Time Exceeded messages from the interface IP address that is facing the source (=you), they are not obligated to do so.

Some routers generally reply from their management address, their loopback address, or some other, depending on configuration.

But the MAC address of 192.168.250.250 is same as 45.150.164.1's.(I made arp requests.)

You don't know that. You only see an IP packet with source 192.168.250.250 coming in a frame with the source MAC address that you associate with 45.150.164.1. It may be simply sourced from that same hop with a different interface's address, or there are two IP addresses bound to the interface facing you, or it may even be routed. You cannot tell.

Does the interface of 45.150.164.1 have two different IP addresses?

That's one possibility. The most likely answer is that the ICMP message is sourced from a different interface on that router.

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You don't mention from where you started the traceroute, so it's hard to give a definite answer. The address block assigned to you (the source addresses of your public-facing servers or your web browsing clients) is often different than the addresses of the links that connect you to your provider.

However, questions about how your ISP provides service are off topic, as are all questions about networks not under your control.

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  • The source of the traceroute is my PC(45.150.164.x). And two different IP addresses are associated with the same mac address.
    – wyb
    Feb 27, 2023 at 16:03
  • Speculation on what your ISP is doing is unfortunately off topic..
    – Ron Trunk
    Feb 27, 2023 at 16:06

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