Problem while establishing ISAKMP in ipsec

Hi,
I am facing problem while setting up ISAKMP between two hosts.
I can see only the Initiator messages but no responder messages in tcpdump. Does anyone know the cause of this behaviour?

FYI, here is the extracted information from tcpdump :
14:47:08.699113 IP 10.118.231.143.isakmp > 10.118.231.130.isakmp: isakmp: phase 1 I ident
14:47:08.699120 IP 10.118.231.130 > 10.118.231.143: icmp 164: 10.118.231.130 udp port isakmp unreachable
14:47:28.610347 IP 10.118.231.143.isakmp > 10.118.231.130.isakmp: isakmp: phase 1 I ident
14:47:28.610353 IP 10.118.231.130 > 10.118.231.143: icmp 164: 10.118.231.130 udp port isakmp unreachable
14:47:53.540184 IP 10.118.231.143.isakmp > 10.118.231.130.isakmp: isakmp: phase 1 I ident
14:47:53.583540 IP 10.118.231.143.isakmp > 10.118.231.130.isakmp: isakmp: phase 1 I ident
14:47:53.626519 IP 10.118.231.143.isakmp > 10.118.231.130.isakmp: isakmp: phase 1 I ident[E]
14:47:53.661367 IP 10.118.231.143.isakmp > 10.118.231.130.isakmp: isakmp: phase 2/others I oakley-quick[E]
14:47:53.705619 IP 10.118.231.143.isakmp > 10.118.231.130.isakmp: isakmp: phase 2/others I oakley-quick[E]

Regards