09-16-2019
What happens when you look at the arp tables, before and after?
On ethernet, as you know, the actual LAN routing is done by MAC address; so when we change IP address, we need to flush / rebuild the arp table (on both ends), generally speaking.
If we change an IP address and do not flush the arp table, there will often be an incorrect IP address <---> MAC address in the arp table and this can cause LAN routing snafus.
PS: I'm writing this based on knowledge from decades ago, off the top of my head, and have not done any research on arp in a long time.
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https://www.unix.com/unix-for-dummies-questions-and-answers/246504-solaris-11-2nd-nic-different-subnet.html
apologies if linking is not appropriate
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ARP(3) Library Functions Manual ARP(3)
NAME
arp - Internet Address Resolution Protocol
SYNOPSIS
bind -a #a /net/arp
/net/arp/ctl
/net/arp/data
/net/arp/stats
DESCRIPTION
The arp device provides the means by which the kernel resolves IP addresses into Ethernet addresses. A cache is maintained by the arp
device to speed the process.
The ctl file controls the ARP cache maintained by the kernel. The flush control message invalidates all entries in the cache. The delete
ipaddr control message invalidates a single cache entry. All IP addresses passed to the system are in the canonical textual form described
in ip(2). The perm ipaddr control message makes an existing cache entry permanent.
When the kernel boots, ipconfig sets up the IP stream and arpd opens #a/arp/data (see ipconfig(8)). This establishes the ARP cache and
enables arpd to receive all ARP packets from the network, which it uses to maintain the cache by writing the results of address resolution
requests back into the cache. The IP stream module uses the cache to translate IP addresses.
Subsequent opens of the data file allow the contents of the cache to be examined. Each cache entry consists of an IP address, an Ethernet
address, and the status of the entry. Entries may be invalid, permanent, or temporary. Permanent entries will never be aged from the
cache. Temporary entries may be replaced by new addresses entered by the ARP server.
The file stats reports the cache performance.
SEE ALSO
ip(3), ipconfig(8)
SOURCE
/sys/src/9/port/devarp.c
ARP(3)