From RPC-PBX-PEO-02:
---------------------
# nmap -v -sV -sU -p 4500-4600 -PU -n -P0 rpc-pbx-per-01
Not shown: 99 closed ports
PORT     STATE SERVICE VERSION
4520/udp open  unknown
4569/udp open  unknown

# ping -c1 rpc-pbx-per-01
PING rpc-pbx-per-01 (10.46.26.252) 56(84) bytes of data.
64 bytes from rpc-pbx-per-01 (10.46.26.252): icmp_seq=1 ttl=64 time=45.0 ms

rpc-pbx-peo-02*CLI> iax2 show peers
rpc-pbx-per-01/  10.46.26.252    (S)  255.255.255.255  4569          UNREACHABLE

iax.conf friend definition:
[rpc-pbx-per-01]
        type=friend
        auth=md5
        host=rpc-pbx-per-01
        secret=rpc-pbx-per-01
        username=rpc-per-01
        trunk=no
        qualify=50
        qualifyfreqok=1000
        qualifyfreqnotok=250
        context=from-iax

-------------------------------------------
From RPC-PBX-PER-01:
-------------------------------------------

rpc-pbx-per-01*CLI> iax2 show peers
rpc-pbx-peo-02/  10.1.1.249      (S)  255.255.255.255  4569          UNREACHABLE

iax.conf friend definition:
[rpc-pbx-peo-02]
        type=friend
        auth=md5
        host=rpc-pbx-peo-02
        secret=rpc-pbx-peo-02
        username=rpc-pbx-peo-02
        trunk=no
        qualify=50
        qualifyfreqok=1000
        qualifyfreqnotok=250
        context=from-iax

# ping -c1 rpc-pbx-peo-02
PING rpc-pbx-peo-02 (10.1.1.249) 56(84) bytes of data.
64 bytes from rpc-pbx-peo-02 (10.1.1.249): icmp_seq=1 ttl=63 time=50.7 ms