WARNING[2753]: chan_sip.c 1735 __sip_xmit

Hi all, I’m new to Asterisk and have just installed it for the first time. I’ve managed to get two ip phones to call each other but now I’m trying to get a connection to the SIP provider (Draytel). Asterisk keeps spewing out the same error message over and over saying:

WARNING[2753]: chan_sip.c 1735 __sip_xmit: sip_xmit of 0x81f32f0 (len 374) to 217.14.132.183:5060 returned -1: Network is unreachable

WARNING[2753]: chan_sip.c 1735 __sip_xmit: sip_xmit of 0x81f2ad0 (len 374) to 217.14.132.183:5060 returned -1: Network is unreachable

Notice[2753]: chan_sip.c 7085 sip_reg_timeout: --registration for ‘*****@draytel.org’ timed out, trying again (attempt #122)

Does anyone know what the problem is ?

Thanks in advance,
Andy.