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Syslog Message id 106023 on PIX 506E VER 6.3(3)

Everything seems to be okay with my firewall but this message keeps appearing in my syslog:
106023 Deny tcp src outside x.x.y.21/25 dist inside x.x.x.149/3559 (or 3556 or 3596 or 3594) by access-group 100. Do need to worry about it? Am I losing some emails?

Here is my config:
fixup protocol dns maximum-length 512
fixup protocol ftp 21
fixup protocol h323 h225 1720
fixup protocol h323 ras 1718-1719
fixup protocol http 80
fixup protocol rsh 514
fixup protocol rtsp 554
fixup protocol sip 5060
fixup protocol sip udp 5060
fixup protocol skinny 2000
no fixup protocol smtp 25
fixup protocol sqlnet 1521
fixup protocol tftp 69
names
access-list 100 permit tcp any host x.x.x.149 eq imap4
access-list 100 permit tcp any host x.x.x.149 eq www
access-list 100 permit tcp any host x.x.x.149 eq pop3
access-list 100 permit icmp any any echo
access-list 100 permit icmp any any echo-reply
access-list 100 permit icmp any any unreachable
access-list 100 permit tcp any host x.x.x.149 eq smtp
pager lines 24
logging on
logging monitor errors
logging host inside 192.168.0.20
icmp permit 192.168.0.0 255.255.255.0 inside
mtu outside 1500
mtu inside 1500
ip address outside x.x.x.149 255.255.255.248
ip address inside 192.168.0.10 255.255.255.0
ip audit info action alarm
ip audit attack action alarm
pdm location 192.168.0.0 255.255.255.248 inside
pdm location 192.168.0.20 255.255.255.255 inside
pdm location 192.168.0.2 255.255.255.255 inside
pdm logging informational 100
pdm history enable
arp timeout 14400
global (outside) 1 interface
nat (inside) 1 0.0.0.0 0.0.0.0 0 0
static (inside,outside) tcp interface imap4 192.168.0.2 imap4 netmask 255.255.25
5.255 0 0
static (inside,outside) tcp interface www 192.168.0.2 www netmask 255.255.255.25
5 0 0
static (inside,outside) tcp interface pop3 192.168.0.2 pop3 netmask 255.255.255.
255 0 0
static (inside,outside) tcp interface smtp 192.168.0.2 smtp netmask 255.255.255.
255 0 0
access-group 100 in interface outside
route outside 0.0.0.0 0.0.0.0 x.x.x.145 1
timeout xlate 0:05:00
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 RADIUS protocol radius
aaa-server LOCAL protocol local
http server enable
http 192.168.0.0 255.255.255.0 inside
no snmp-server location
no snmp-server contact
snmp-server community public
no snmp-server enable traps
floodguard enable
telnet 192.168.0.0 255.255.255.0 inside
telnet timeout 5
ssh timeout 5
console timeout 5
dhcpd address 192.168.0.11-192.168.0.254 inside
dhcpd lease 3600
dhcpd ping_timeout 750
dhcpd auto_config outside
terminal width 80
banner motd UNAUTHORISED ACCESS PROHIBITED
Cryptochecksum:1805e5096398c27f52c529e83bc022ff
: end
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sarit2002
Asked:
sarit2002
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2 Solutions
 
srikrishnakCommented:
If i am not wrong your mail server address is X.X.X.149..When your internal client initiates a connection on SMTP (25) on the destination side it takes a random port. When the reply comes the source port will be the "random port" and destination will be "25"..
Normally the reply and responce will be treated as a single session thus not dropping the responce packets...But this case it seems like due to some reason(most of the time asynchronous routing or state table sync problem ifyou have redundancy) the reply packet was not matched with a initial request packet..So the firewall assumes that this was illegal n droppes...
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sarit2002Author Commented:
My pix is connected to the ISP router on the external interface. Mails seem to be flowing okay but this message worries me. What can I do?
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srikrishnakCommented:
I dont think so its a cause of concern..Mostly its due to some session issue..I see this kind of behaviour with CheckPoint quite often...They attribute to a session stuck....
And you wont be having any problems with mails normally...coz its only one session..To furthur explore try to sniff on the source machine using ethereal to confirm that the issue exists...
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srikrishnakCommented:
Another thing is try checking the default timeout value for TCP n UDP session...If this is not default n reduced then try making it to default..
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sarit2002Author Commented:
How you check the session timeout??
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lrmooreCommented:
>timeout xlate 0:05:00
>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

All of the above timeouts are default and should be just fine. 5 minutes for an xlate and 1 hour for a connection should be more than enough time to close out any session.
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