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'show ip arp' intended functionality
Hello,

This is more of a curiosity rather than an actual technical question.

How *should* the command 'show ip arp' function?

I've noticed that on almost all network operating systems the 'show ip arp' command (or it's equivalent) shows the device (router/switch/whatever) in the table.

On NX-OS and Dell 10 Enterprise it only shows the hosts connected to the interface (and not switch/routers own IP)

I am mostly just curious as to "what is correct" also if anyone is aware of a command in NX-OS or Dell 10 E that shows it 'the old way' please enlighten me!

Thanks,
-Drew

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Re: 'show ip arp' intended functionality [ In reply to ]
On 28/10/2021 13:53, Drew Weaver wrote:
> Hello,
>
> This is more of a curiosity rather than an actual technical question.
>
> How *should* the command 'show ip arp' function?
>
> I've noticed that on almost all network operating systems the 'show ip arp' command (or it's equivalent) shows the device (router/switch/whatever) in the table.
>
> On NX-OS and Dell 10 Enterprise it only shows the hosts connected to the interface (and not switch/routers own IP)
>
> I am mostly just curious as to "what is correct" also if anyone is aware of a command in NX-OS or Dell 10 E that shows it 'the old way' please enlighten me!
>
I would expect it to show the table of IP addresses and MAC addresses
that it has learned via the ARP protocol. Static ARP entries (using
configured and BIA MAC addresses) I wouldn't expect to see, unless
labelled as "static" as opposed to "dynamic".

--
Giles Coochey

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Re: 'show ip arp' intended functionality [ In reply to ]
Oh sorry I should've been more specific.

On Dell OS10E and NX-OS:

In the case of
Vlan 145
Int vlan 145
Ip address 10.1.0.1/29

sh ip arp vlan 145 only shows 10.1.0.2, 10.1.0.3 but never the router's own ip/MAC address in the arp table.

I was just trying to determine whether the 'right way' is how it used to work (where it showed the router's own IP/mac in the arp table) or if the right way is how it is done now.

Thanks,
-Drew

-----Original Message-----
From: Gustaf Hyllested Servé <gustaf@serve.dk>
Sent: Thursday, October 28, 2021 9:15 AM
To: Drew Weaver <drew.weaver@thenap.com>; cisco-nsp@puck.nether.net
Subject: Re: [c-nsp] 'show ip arp' intended functionality

Show ip arp, returns the learned (or configured) mappings between MAC-addresses and IP-addresses that the network-stack communicates with. So a layer2 switch probably only show it's default gateway and other devices that the management-plane have communicated with. A local router (or "layer 3 switch") will at most times have all (active) devices on the networks it serves in its arp-table.

Gustaf Hyllested Serve


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Re: [External] 'show ip arp' intended functionality [ In reply to ]
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