Archives for category: Palo Alto

When troubleshooting traffic flows through the Palo Alto NGFW, it can be difficult to see what’s happening. Using the logs from the GUI can help.

An alternative is, to use the command line “show session all filter destination [IP]“. This shows you a filtered view of stateful sessions going through the firewall. It provides information like state, source/destination, translated IP/Port. An example is shown below. (Use the context sensitive help if you need more options)

admin@PA-FW> show session all filter destination 74.200.26.232

--------------------------------------------------------------------------------
ID Application State Type Flag Src[Sport]/Zone/Proto (translated IP[Port])
Vsys Dst[Dport]/Zone (translated IP[Port])
--------------------------------------------------------------------------------
37167 web-browsing ACTIVE FLOW *NS 192.168.20.115[55927]/trust/6 (1.1.1.1[40416])
vsys1 74.200.26.232[443]/untrust (74.200.26.232[443])

Once you have the session ID (in the case above the session ID is 37167), use the command “show session id 37167” to drill down further into the information within that session.

admin@PA-FW> show session id 37167
Session 37167

c2s flow:
 source: 192.168.20.115 [trust]
 dst: 74.200.26.232
 proto: 6
 sport: 55927 dport: 443
 state: ACTIVE type: FLOW
 src user: test\robert
 dst user: unknown
 qos node: ethernet1/1, qos member Qid 0
 match src interface: any
 match src address: ('any ',)

s2c flow:
 source: 74.200.26.232 [untrust]
 dst: 1.1.1.1
 proto: 6
 sport: 443 dport: 40416
 state: ACTIVE type: FLOW
 src user: unknown
 dst user: test\robert

start time : Fri Jan 26 10:03:53 2018
 timeout : 60 sec
 time to live : 48 sec
 total byte count(c2s) : 1924
 total byte count(s2c) : 5115
 layer7 packet count(c2s) : 14
 layer7 packet count(s2c) : 10
 vsys : vsys1
 application : web-browsing
 rule : Rule 2
 session to be logged at end : True
 session in session ager : True
 session synced from HA peer : False
 address/port translation : source + destination
 nat-rule : NAT-Outside(vsys1)
 layer7 processing : completed
 URL filtering enabled : True
 URL category : Rule 2
 session via syn-cookies : False
 session terminated on host : False
 session traverses tunnel : False
 captive portal session : False
 ingress interface : ethernet1/2
 egress interface : ethernet1/1
 session QoS rule : N/A (class 4)
 tracker stage l7proc : proxy timer expired

As you can see above, the amount of information can be very helpful for troubleshooting. If you suspect a particular session is causing a problem, you can clear with the command “clear session ID 37167

RH

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This feature is similar to Cisco IPSLA, in that it tracks the reachability of a destination and can remove static routes based on the ping response.

Simple topology with Palo-Alto connected to the internet and using path monitor on the default route. Internal interface peering OSPF with the core router and redistributing the static route but only when the ping responds.

Capture

 

 

 

 

 

 

 

 

 

First create the static route
Network -> Virtual Routers -> (router) -> Static Routes -> Add+

Virtual Router - Static Routes

In this scenario the path monitor will ping the opposite side of the link and Google DNS, both must fail for the condition to be met. Interval and count are default (5 pings 3 seconds apart). Once the pings fail, the route will be removed from the routing table. When the router is able to ping the destination after a failure it waits 2 minutes before re-installing the route, this is default preemptive behaviour and can be changed.

Next create a redistribution profile that redistributes your routes, what I found was that if you redistribute ‘0.0.0.0/0’ that means all routes, if you have other routes you don’t want to redistribute just match them with a lower priority and choose ‘No redist

Network -> Virtual Routers -> (router) -> Redistribution Profile -> Add+

Redistribution Profile

Configure OSPF as you normally would with any other device no difference here the usual attributes must match. Area 0 is the same as Area 0.0.0.0.

Next apply the redistribution profile to OSPF and check ‘Allow Redistribute Default Route‘. You have the option to set external type, metric and tag.

Network -> Virtual Routers -> (router) -> OSPF -> Export Rules -> Add+

Export Rules

The Palo-Alto should have formed neighbors with the core router and be redistributing the default route. This can be seen here. Network -> Virtual Routers -> More Runtime Stats. You can also view the routing table here and the forwarding table along with OSPF neighbors etc.

Run Time Stats

Currently the core router receives the route from the Palo-Alto

Core

Next fail the routing on the internet router to see the impact on the path monitoring. The outcome is, the route is withdrawn (debug ip routing)

Route withdrawn

Path Monitor (down)

On the core device you may have a floating static or default route with a higher metric from a different IGP, waiting to take over in the event of a failure to the Palo-Alto.

When routing is restored you can view the preempted route counting down. After the 2 minutes the route is re-instated.

Preempt hold

That’s it, works great.

RH