Create a Post
cancel
Showing results for 
Search instead for 
Did you mean: 
Highlighted
Iron

Connection Table

Hi All,

I am curious to know more about the connection table entries. I have referred the SK65133 but I could see only the details about HEXA representation.

It would me more helpful if some one attempts to decode the connection table.

I have a windows PC (10.10.10.10) initiating an ICMP request toward 4.2.2.2 and at firewall I have configured Source NAT (Hide) and Destination NAT(Static).

My source (10.10.10.10) will be NAT to 192.168.20.10 and Destination (4.2.2.2) will be NAT to 8.8.8.8.

Below is the output of "fw tab -t connections -u -f"

10:40:18 5 N/A N/A 10.0.0.101 > N/A LogId: <max_null>; ContextNum: <max_null>; OriginSicName: <max_null>; : -----------------------------------(+); Direction: 0; Source: 8.8.8.8; SPort: 0; Dest: 192.168.20.10; DPort: 26670; Protocol: icmp; CPTFMT_sep_1: ->; Direction_1: 0; Source_1: 10.10.10.10; SPort_1: 1; Dest_1: 4.2.2.2; DPort_1: 0; Protocol_1: icmp; FW_symval: 2054; LastUpdateTime: 25Jun2020 10:40:18; ProductName: VPN-1 & FireWall-1; ProductFamily: Network;

10:40:18 5 N/A N/A 10.0.0.101 > N/A LogId: <max_null>; ContextNum: <max_null>; OriginSicName: <max_null>; : -----------------------------------(+); Direction: 1; Source: 8.8.8.8; SPort: 0; Dest: 10.10.10.10; DPort: 1; Protocol: icmp; CPTFMT_sep_1: ->; Direction_2: 0; Source_2: 10.10.10.10; SPort_2: 1; Dest_2: 4.2.2.2; DPort_2: 0; Protocol_2: icmp; FW_symval: 2053; LastUpdateTime: 25Jun2020 10:40:18; ProductName: VPN-1 & FireWall-1; ProductFamily: Network;

10:40:18 5 N/A N/A 10.0.0.101 > N/A LogId: <max_null>; ContextNum: <max_null>; OriginSicName: <max_null>; : -----------------------------------(+); Direction: 0; Source: 10.10.10.10; SPort: 1; Dest: 4.2.2.2; DPort: 0; Protocol: icmp; CPTFMT_sep: ;; Type: 65537; Rule: 4; Timeout: 353; Handler: 0; Ifncin: 2; Ifncout: 2; Ifnsin: 3; Ifnsout: 3; Bits: 0000780000000000; NAT_VM_Source: 10.10.10.10; NAT_VM_SPort: 1; NAT_VM_Dest: 8.8.8.8; NAT_VM_DPort: 0; NAT_VM_Flags: 44; NAT_Client_Source: ; NAT_Client_SPort: 0; NAT_Client_Dest: 4.2.2.2; NAT_Client_DPort: 0; NAT_Client_Flags: 44; NAT_Server_Source: 192.168.20.10; NAT_Server_SPort: 26670; NAT_Server_Dest: ; NAT_Server_DPort: 0; NAT_Server_Flags: 1049132; NAT_Xlate_Flags: 1605644; Expires: 26/30; LastUpdateTime: 25Jun2020 10:40:18; ProductName: VPN-1 & FireWall-1; ProductFamily: Network;

10:40:18 5 N/A N/A 10.0.0.101 > N/A LogId: <max_null>; ContextNum: <max_null>; OriginSicName: <max_null>; : -----------------------------------(+); Direction: 1; Source: 10.10.10.10; SPort: 1; Dest: 8.8.8.8; DPort: 0; Protocol: icmp; CPTFMT_sep_1: ->; Direction_1: 0; Source_1: 10.10.10.10; SPort_1: 1; Dest_1: 4.2.2.2; DPort_1: 0; Protocol_1: icmp; FW_symval: 2050; LastUpdateTime: 25Jun2020 10:40:18; ProductName: VPN-1 & FireWall-1; ProductFamily: Network;

 

---------------------------------------------------------------------------------------------------------------------------------

 

Can you please indicate which one is S-link entry and which one is Real Connection entry, and whet does the field in the entry mean.

0 Kudos
2 Replies
Highlighted
Admin
Admin

There are different entries created for the different iterations of NAT and non-NAT IPs.
I don't know that knowing what an S-link entry is is that relevant (or at least I've never found it to be relevant in Troubleshooting).
The port numbers are zero because this is ICMP which doesn't use port numbers.
0 Kudos
Highlighted

In the connections table, what would be considered a "connection" is actually being tracked as at least two separate packet flows by the firewall, that show up on different lines of the fw tab -t connections -u -f command.  The SLINK is used to symbolically link the individual table entries together as a "connection".

For a connection that is not NATed there are two separate flows tracked:

  • c2s (client to server)
  • s2c (server to client)

For a connection that is NATed there are four separate flows tracked:

  • c2s (client to server) pre-NAT
  • c2s (client to server) post-NAT
  • s2c (server to client) pre-NAT
  • s2c (server to client) post-NAT

Rather than trying to interpret all of this, I'd suggest using the old but only recently-documented fw ctl conntab command which shows a connection-oriented list rather than individual packet flows.

R80.40 addendum for book "Max Power 2020" now available
for free download at http://www.maxpowerfirewalls.com
0 Kudos