Cisco Systems PIX 6.3.4 - I have question on a VPN setup & ICMP

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Subject Author Date
PIX 6.3.4 - I have question on a VPN setup & ICMP Ralph (c) 08-26-05
Posted by Ralph (c) on August 26, 2005, 11:08 am
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Hello,

I have questions on a VPN setup & ICMP

1. Let me show you this line,

isakmp key ******** address 195.238.208.162 netmask 255.255.255.255
no-xauth no-config-mode

no-xauth no-config-mode, what does it mean? when do I have to use it?

2. The inside networks being hide-nated to get to the internet need to
be able to ping the whole internet. But, doing it, the external IP of
the firewall is pingable as well. In my particular case, how do I
restrict the firewall to be pinged while allowing the networks behind to
get the request and the replies to echo? I know there is an URL on
cisco.con explaining how to handle ICMP but I do not understand it! and
it does not work either!

3. Let me show you those lines:

crypto map vpn-map 1 ipsec-isakmp
crypto map vpn-map 1 match address r55
crypto map vpn-map 1 set peer 195.238.208.162
crypto map vpn-map 1 set peer 195.238.108.163
crypto map vpn-map 1 set transform-set trans-r55

We've got two peers in there! Could you tell me when we can use it and
why? How does PIX know the first is dead?

Thank you!

PS: IP in there are fake.

/ralph

pix(config)# sh conf
: Saved
: Written by enable_15 at 08:26:03.431 UTC Fri Aug 26 2005
PIX Version 6.3(4)
interface ethernet0 100full
interface ethernet1 100full
nameif ethernet0 external security0
nameif ethernet1 inside security100
enable password ... encrypted
passwd ... encrypted
hostname pix
domain-name brussels.lan
fixup protocol dns maximum-length 512
.....
fixup protocol tftp 69
names
access-list to_wild_outside permit udp any any eq domain
access-list to_wild_outside permit tcp any any eq ssh
access-list to_wild_outside permit tcp any any eq www
access-list to_wild_outside permit tcp any any eq https
access-list to_wild_outside permit tcp any any eq ftp
access-list to_wild_outside permit icmp any any
access-list to_wild_outside permit tcp any host 195.238.90.8 eq 5223
access-list to_wild_outside permit tcp any host 195.238.90.9 eq 706
access-list to_wild_outside remark ------------------------
access-list remote-syslog permit ip interface external host 195.218.198.163
access-list nat0 remark
----------------------------------------------------------
access-list nat0 permit ip 10.140.20.0 255.255.255.0 192.168.19.0
255.255.255.240
access-list nat0 permit ip 10.140.20.0 255.255.255.0 192.168.18.128
255.255.255.224
access-list nat0 permit ip 10.140.20.0 255.255.255.0 192.168.15.0
255.255.255.0
access-list nat0 permit ip 10.140.20.0 255.255.255.0 192.168.16.0
255.255.255.0
access-list nat0 permit ip 10.140.20.0 255.255.255.0 192.168.17.0
255.255.255.0
access-list nat0 permit ip 10.140.20.0 255.255.255.0 192.168.21.0
255.255.255.0
access-list nat0 permit ip 192.168.19.0 255.255.255.240 10.140.20.0
255.255.255.0
access-list nat0 permit ip 192.168.18.128 255.255.255.224 10.140.20.0
255.255.255.0
access-list nat0 permit ip 192.168.15.0 255.255.255.0 10.140.20.0
255.255.255.0
access-list nat0 permit ip 192.168.16.0 255.255.255.0 10.140.20.0
255.255.255.0
access-list nat0 permit ip 192.168.17.0 255.255.255.0 10.140.20.0
255.255.255.0
access-list nat0 permit ip 192.168.21.0 255.255.255.0 10.140.20.0
255.255.255.0
access-list nat0 remark
----------------------------------------------------------
access-list r55 remark
----------------------------------------------------------
access-list r55 permit ip 192.168.19.0 255.255.255.240 10.140.20.0
255.255.255.0
access-list r55 permit ip 192.168.18.128 255.255.255.224 10.140.20.0
255.255.255.0
access-list r55 permit ip 192.168.15.0 255.255.255.0 10.140.20.0
255.255.255.0
access-list r55 permit ip 192.168.16.0 255.255.255.0 10.140.20.0
255.255.255.0
access-list r55 permit ip 192.168.17.0 255.255.255.0 10.140.20.0
255.255.255.0
access-list r55 permit ip 192.168.21.0 255.255.255.0 10.140.20.0
255.255.255.0
access-list r55 remark
----------------------------------------------------------
access-list external_if permit icmp any host 212.217.18.76
no pager
logging on
logging timestamp
logging buffered informational
logging trap informational
logging host external 195.218.198.163
icmp permit any echo-reply external
icmp permit host 195.218.198.163 external
icmp permit host 195.238.208.162 external
icmp permit host 195.238.108.163 external
icmp permit any echo-reply inside
mtu external 1500
mtu inside 1500
ip address external 212.217.18.76 255.255.255.252
ip address inside 192.168.19.3 255.255.255.240
ip audit info action alarm
ip audit attack action alarm
pdm location 195.238.19.8.40 255.255.255.255 external
pdm location 195.238.19.8.41 255.255.255.255 external
pdm location 212.68.250.173 255.255.255.255 external
pdm history enable
arp timeout 14400
global (external) 1 interface
nat (inside) 0 access-list nat0
nat (inside) 1 access-list to_wild_outside 0 0
access-group external_if in interface external
route external 0.0.0.0 0.0.0.0 57.67.28.125 1
route inside 10.150.79.0 255.255.255.224 192.168.19.1 1
route inside 10.150.103.240 255.255.255.248 192.168.19.1 1
route inside 10.150.140.0 255.255.255.224 192.168.19.1 1
route inside 10.5.64.0 255.255.255.0 192.168.19.1 1
route inside 10.43.233.0 255.255.255.128 192.168.19.1 1
route inside 10.53.39.144 255.255.255.252 192.168.19.1 1
route inside 10.35.115.144 255.255.255.240 192.168.19.1 1
route inside 192.168.15.0 255.255.255.0 192.168.19.1 1
route inside 192.168.16.0 255.255.255.0 192.168.19.1 1
route inside 192.168.17.0 255.255.255.0 192.168.19.1 1
route inside 192.168.18.128 255.255.255.224 192.168.19.1 1
route inside 192.168.21.0 255.255.255.0 192.168.19.1 1
timeout xlate 3:00:00
timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 rpc 0:10:00 h225
1:00:00
timeout h323 0:05:00 mgcp 0:05:00 sip 0:30:00 sip_media 0:02:00
timeout uauth 0:05:00 absolute
aaa-server TACACS+ protocol tacacs+
aaa-server TACACS+ max-failed-attempts 3
aaa-server TACACS+ deadtime 10
aaa-server RADIUS protocol radius
aaa-server RADIUS max-failed-attempts 3
aaa-server RADIUS deadtime 10
aaa-server LOCAL protocol local
ntp server 195.238.87.3.167 source external
http server enable
http 195.238.19.8.40 255.255.255.255 external
http 195.238.19.8.41 255.255.255.255 external
http 212.68.250.173 255.255.255.255 external
snmp-server host external 195.238.87.3.10 poll
snmp-server host external 195.238.87.3.11 poll
no snmp-server location
no snmp-server contact
snmp-server community .........
no snmp-server enable traps
floodguard enable
sysopt connection permit-ipsec
crypto ipsec transform-set trans-aes-md5 esp-aes esp-md5-hmac
crypto ipsec transform-set trans-3des-sha esp-3des esp-sha-hmac
crypto ipsec transform-set trans-r55 esp-3des esp-md5-hmac
crypto ipsec transform-set trans-aes-sha esp-aes esp-sha-hmac
crypto map vpn-map 1 ipsec-isakmp
crypto map vpn-map 1 match address r55
crypto map vpn-map 1 set peer 195.238.208.162
crypto map vpn-map 1 set peer 195.238.108.163
crypto map vpn-map 1 set transform-set trans-r55
crypto map vpn-map 2 ipsec-isakmp
crypto map vpn-map 2 match address remote-syslog
crypto map vpn-map 2 set peer 195.218.198.163
crypto map vpn-map 2 set transform-set trans-aes-sha
crypto map vpn-map interface external
isakmp enable external
isakmp key ******** address 195.238.208.162 netmask 255.255.255.255
no-xauth no-config-mode
isakmp key ******** address 195.238.108.163 netmask 255.255.255.255
no-xauth no-config-mode
isakmp key ******** address 195.218.198.163 netmask 255.255.255.255
no-xauth no-config-mode
isakmp identity address
isakmp policy 1 authentication pre-share
isakmp policy 1 encryption aes-256
isakmp policy 1 hash md5
isakmp policy 1 group 2
isakmp policy 1 lifetime 86400
isakmp policy 2 authentication pre-share
isakmp policy 2 encryption 3des
isakmp policy 2 hash sha
isakmp policy 2 group 2
isakmp policy 2 lifetime 86400
isakmp policy 3 authentication pre-share
isakmp policy 3 encryption 3des
isakmp policy 3 hash sha
isakmp policy 3 group 2
isakmp policy 3 lifetime 36000
isakmp policy 4 authentication pre-share
isakmp policy 4 encryption 3des
isakmp policy 4 hash md5
isakmp policy 4 group 2
isakmp policy 4 lifetime 36000
telnet timeout 5
....
ssh timeout 60
console timeout 0
terminal width 80
Cryptochecksum:...............
pix(config)#


Posted by Walter Roberson on August 26, 2005, 3:17 pm
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:1. Let me show you this line,

:isakmp key ******** address 195.238.208.162 netmask 255.255.255.255 no-xauth
no-config-mode

:no-xauth no-config-mode, what does it mean? when do I have to use it?

http://www.cisco.com/univercd/cc/td/doc/product/iaabu/pix/pix_sw/v_63/cmdref/gl.htm#wp1027312

  Both the Xauth and IKE Mode Configuration features are specifically
  designed for remote VPN clients. The Xauth feature allows the PIX
  Firewall to challenge the peer for a username and password during
  IKE negotiation. The IKE Mode Configuration enables the PIX
  Firewall to download an IP address to the peer for dynamic IP
  address assignment. Most security gateways do not support the Xauth
  and IKE Mode Configuration features.



:2. The inside networks being hide-nated to get to the internet need to
:be able to ping the whole internet. But, doing it, the external IP of
:the firewall is pingable as well.

icmp traffic -to- the PIX is controlled by the 'icmp' command,
not by access-lists. If you do not configure an 'icmp' command then
the default is to permit all icmp.


:3. Let me show you those lines:

:crypto map vpn-map 1 ipsec-isakmp
:crypto map vpn-map 1 match address r55
:crypto map vpn-map 1 set peer 195.238.208.162
:crypto map vpn-map 1 set peer 195.238.108.163
:crypto map vpn-map 1 set transform-set trans-r55

:We've got two peers in there! Could you tell me when we can use it and
:why?

http://www.cisco.com/univercd/cc/td/doc/product/iaabu/pix/pix_sw/v_63/cmdref/c.htm#wp1034654

  For ipsec-isakmp crypto map entries, you can specify multiple peers
  by repeating this command. The peer that packets are actually sent
  to is determined by the last peer that the PIX Firewall received
  either traffic or a negotiation request from for a given data flow.
  If the attempt fails with the first peer, IKE tries the next peer
  on the crypto map list.


:How does PIX know the first is dead?

isakmp keep-alives stop being received, and isakmp probes go unanswered
within a reasonable timeout.
--
   Entropy is the logarithm of probability   -- Boltzmann


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