Sip2Sip Conf and Errors

username=223XXXXXX
type=peer
canreinvite=no
secret=XXXXXX
qualify=yes
nat=yes
insecure=invite,port
disallow=all
host=sip2sip.info
domain=sip2sip.info
fromdomain=sip2sip.info
outboundproxy=proxy.sipthor.net
fromuser=223XXXXXX
defaultuser=223XXXXXX
dtmfmode=rfc2833
context=from-trunk
allow=ulaw&gsm


223XXXXXX:[email protected]/223XXXXXX


echo "enable=yes" >> /etc/asterisk/dnsmgr.conf
echo "srvlookup=yes" >> /etc/asterisk/sip_general_custom.conf


vps10*CLI> sip show registry
Host                                    dnsmgr Username       Refresh State                Reg.Time
sip2sip.info:5060                       N      223XXXXXX         120 Unregistered
1 SIP registrations.


root@vps10:~ $ tcpdump dst 85.17.186.7 -vv
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes
23:51:07.984858 IP (tos 0x60, ttl 64, id 13319, offset 0, flags [none], proto UDP (17), length 559)
    vps10.sip > node07.dns-hosting.info.sip: [bad udp cksum c03!] SIP, length: 531
        OPTIONS sip:sip2sip.info SIP/2.0
        Via: SIP/2.0/UDP 174.XXX.XXX.XXX:5060;branch=z9hG4bK2093600e;rport
        Max-Forwards: 70
        From: "Unknown" <sip:[email protected]>;tag=as15746292
        To: <sip:sip2sip.info>
        Contact: <sip:[email protected]:5060>
        Call-ID: [email protected]:5060
        CSeq: 102 OPTIONS
        User-Agent: FPBX-2.11.0(11.4.0)
        Date: Fri, 23 Aug 2013 04:51:07 GMT
        Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO, PUBLISH
        Supported: replaces
        Content-Length: 0