Lol Bad Ping

[Pierpont Oldham]

pingis a computer network administration software utility used to test the reachability of a host on an Internet Protocol (IP) network. It is available for virtually all operating systems that have networking capability, including most embedded network administration software.

Ping measures the round-trip time for messages sent from the originating host to a destination computer that are echoed back to the source. The name comes from active sonar terminology that sends a pulse of sound and listens for the echo to detect objects under water.[1]

Ping operates by means of Internet Control Message Protocol (ICMP) packets. Pinging involves sending an ICMP echo request to the target host and waiting for an ICMP echo reply. The program reports errors, packet loss, and a statistical summary of the results, typically including the minimum, maximum, the mean round-trip times, and standard deviation of the mean.

The command-line options of the ping utility and its output vary between the numerous implementations. Options may include the size of the payload, count of tests, limits for the number of network hops (TTL) that probes traverse, interval between the requests and time to wait for a response. Many systems provide a companion utility ping6, for testing on Internet Protocol version 6 (IPv6) networks, which implement ICMPv6.

The ping utility was written by Mike Muuss in December 1983 during his employment at the Ballistic Research Laboratory, now the US Army Research Laboratory. A remark by David Mills on using ICMP echo packets for IP network diagnosis and measurements prompted Muuss to create the utility to troubleshoot network problems.[1] The author named it after the sound that sonar makes, since its methodology is analogous to sonar's echolocation.[1][2] The backronym Packet InterNet Groper for PING has been used for over 30 years,[timeframe?] and although Muuss says that from his point of view PING was not intended as an acronym, he has acknowledged Mills' expansion of the name.[1][3] The first released version was public domain software; all subsequent versions have been licensed under the BSD license. Ping was first included in 4.3BSD.[4] The FreeDOS version was developed by Erick Engelke and is licensed under the GPL.[5] Tim Crawford developed the ReactOS version. It is licensed under the MIT License.[6]

The output lists each probe message and the results obtained. Finally, it lists the statistics of the entire test. In this example, the shortest round trip time was 9.674 ms, the average was 10.968 ms, and the maximum value was 11.726 ms. The measurement had a standard deviation of 0.748 ms.

In cases of no response from the target host, most implementations display either nothing or periodically print notifications about timing out. Possible ping results indicating a problem include the following:

In case of error, the target host or an intermediate router sends back an ICMP error message, for example host unreachable or TTL exceeded in transit. In addition, these messages include the first eight bytes of the original message (in this case header of the ICMP echo request, including the quench value), so the ping utility can match responses to originating queries.[8]

The Identifier and Sequence Number can be used by the client to match the reply with the request that caused the reply. In practice, most Linux systems use a unique identifier for every ping process, and sequence number is an increasing number within that process. Windows uses a fixed identifier, which varies between Windows versions, and a sequence number that is only reset at boot time.

The payload of the packet is generally filled with ASCII characters, as the output of the tcpdump utility shows in the last 32 bytes of the following example (after the eight-byte ICMP header starting with 0x0800):

The payload may include a timestamp indicating the time of transmission and a sequence number, which are not found in this example. This allows ping to compute the round trip time in a stateless manner without needing to record the time of transmission of each packet.

The payload may also include a magic packet for the Wake-on-LAN protocol, but the minimum payload, in that case, is longer than shown. The Echo Request typically does not receive any reply if the host was sleeping in hibernation state, but the host still wakes up from sleep state if its interface is configured to accept wakeup requests. If the host is already active and configured to allow replies to incoming ICMP Echo Request packets, the returned reply should include the same payload. This may be used to detect that the remote host was effectively woken up, by repeating a new request after some delay to allow the host to resume its network services. If the host was just sleeping in low power active state, a single request wakes up that host just enough to allow its Echo Reply service to reply instantly if that service was enabled. The host does not need to wake up all devices completely and may return to low-power mode after a short delay. Such configuration may be used to avoid a host to enter in hibernation state, with much longer wake-up delay, after some time passed in low power active mode.[citation needed]

Issue I'm having is I can't ping the firewall from the internet. I confirmed internet access by going to the Troubleshooting section in the GUI and successfully pinging 4.2.2.2 and tracing to other internet destinations.

I'm actually trying to enable ping for the untrust interface so that the public side can be pinged on the internet. I'd preferably like to have an access list to only allow my monitoring application to receive ping replies from the firewall.

So if I implement the access-list allowing ping, is there an implicity deny all at the end or will I be fine for all other traffic? I currently have an ipsec site to site vpn tunnel terminating on the outside so I wouldn't want to disrupt that. Just want to be sure.

The filter has a third term that will allow all other traffic to be accepted and processed. There is always that default term to discard all at the end, hence the third term to allow all other traffic.

However you want to use the "commit confirm 5" (use whatever time value you think is long enough to test; this is five minutes) when applying firewall filters and even more so especially when it is your external interfaces.

Currently we have a Guest Wireless network setup behind our PA. We'd like to use this network as a test network as well, for certain projects we are working on, to act as if it was outside the network. I have done this in the past with other vendor firewalls but I have not been successful in making this happen on a Palo Alto.

Right now, when I connect to this network I am unable to ping the public IP address of the PA firewall. Management is configured to allow ping on that interface. NAT rules and policy based forwarding look okay too.

To make ping work you will probably need to create a mgmt-profile (only containing ping) which you attach to untrust and then a security rule which will allow the U-turn NAT to ping this interface from the other zone.

I appreciate the help everybody. Thanks Steven your explanation and example, it helped me understand the problem and fix it. I am now able to ping the PA public IP address from inside the untrust Guest Wifi network as well as still get out to the internet. In the end I created two NATs. 1 for outbound traffic and one for traffic to the PA public IP address (Uturn NAT ). Just as a reference for others who may wander upon this discussion I've added a screen shot of my configs. The parts I blacked out are the places I added the public IP address of the untrust interface for my internet connection (the public IP I am attempting to ping).

I have tried a lot, and at this point I think I just must be missing something obvious that for whatever reason wont come to mind. From the PA3050 I can not ping outbound from the public IP. When I run captures, all outbound traffic is in dropped stage. There is no network functionality at all, and I am unable to find the issue.

Thank you so much for the help, but I fixed it all! It was some issues with subnetting and a few with routing, but worked them all out. I would go in detail, but it was in no way related to nat or security.

I am aware of how to ping, but its just not working. I enabled logging oneven more of the security policies and saw what I have seen before in the traffic tab. Connections seem to never complete and they always age out and application is left incomplete. I am unsure of where to go from here as this issue has left me quite confused. Whether it is an issue with NAT, Security, or some other rule, I need some help sorting this out.

They dont match mine, but they match intrazone which should let them through, right? Or due to intrazone being intra would it block it from finishing session with the external host? Also sorry, but the results are the same internally as well.

Ping is not disabled, and ARP is incomplete on resolving. I recall seeing in either recieve or drop packet captures, ARP packets defining what the next hop's MAC was. Also another thing to note is my interface is a eth channel, but this issue was happening before as well.

In regards to the dual link, in simplest terms, yes. However, in reality we own a /28 range and have a central router for just this range. From that router we have 2 links to a firewall plugged in for production networks, and another 2 links to the palo alto. Both of these firewalls have different public IPs.

I'm coming from a Cisco ASA background and am finding the monitoring/logging on the UTM to be a bit difficult. On the ASA I could look a the syslog and see live monitoring of ALL traffic. Then filter accordingly.

The specific thing I'm looking for now is the ability to monitor pings (ICMP). Being as you have to set up ping in the firewall rules I'd think the firewall live log would be the place to look. Well I must be thinking wrong because it is showing neither successful nor non-successful ping traveling from the LAN to the WAN.

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