# CARP with or without Interface IPs



## tpfiler (Feb 3, 2020)

Hello,

I have a carp setup with standard configurations and Master Backup work as expected, for example:
in *PC1 */etc/rc.conf
ifconfig_em0="inet 1.1.1.*2* netmask 255.255.255.240"
ifconfig_em0_alias0="inet vhid 1 advskew 100 pass test alias 1.1.1.*1*/32"

in *PC2* /etc/rc.con
ifconfig_em0="inet 1.1.1.*3* netmask 255.255.255.240"
ifconfig_em0_alias0="inet vhid 1 advskew 200 pass test alias 1.1.1.*1*/32"

PC1 became Master and PC2 became Backup

Now I am attempting to provided redundancy using the same interfaces em0 of the same PC1 and PC2 for a different network.
Do I need another *alias *interface ip for the interface and then the *alias *for the virtual IP simultaneously?

This is what I have that is working, I think.

I added 1st:

to PC*1* /etc/rc.conf
ifconfig_em0_alias1="inet 172.16.1.*6* netmask 255.255.255.*240*"
ifconfig_em0_alias2="inet vhid 2 advskew 100 pass test alias 172.16.1.*5*/28"

to PC*2* /etc/rc.conf
ifconfig_em0_alias1="inet 172.16.1.*7* netmask 255.255.255.*240*"
ifconfig_em0_alias2="inet vhid 2 advskew 200 pass test alias 172.16.1.*5*/28"

I know the manual says to provide a /32 ip for carp ip but when I tried it the carp master and backup were selected but when I tried to ping the carp ip on the backup it kept telling me the host was down but the master could ping the carp ip, hence the /28.

I can ping all but I want to make sure what I am doing will not fail in production.

Thank you!


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