1, the PIX placed in a fixed IP environment (external network for fixed IP), and set the correct ACL allow ICMP release, this case intranet can be normal Internet access can also ping the extranet.
2, and then put the PIX in the ADSL environment (with PIX to dial), ACL or before the same, PIX under the intranet computer can only surf the internet, can not ping the extranet.
The problem is due to the fact that PIX is not open to an audit of ICMP and needs to use the command fixup protocol ICMP for ICMP audit and release.
Pix (config) # Fixup protocol ICMP/In fact, only this command is required, no more ACL release.
But as for why in the fixed IP environment can ping the outside network directly?? In the fixed IP environment also did not open ICMP audit Ah! It seems that the PIX security features are worth further study.
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