[Ping Eye 2 Serial Number Lookup
Saija Grzegorek
While troubleshooting an occasional network "stall" on my home internet, I came across this technical tip from Dell. They suggest using ping -n to avoid a stall caused by DNS resolution. This got me thinking, what does the -n switch actually do? It seems to me that DNS resolution is required if you ping a DNS name, but not required if you ping an IP.
inet_aton converts from the IPv4 numbers-and-dots notation into binary form. It returns 1 on success. If the last argument given to ping can be converted, the fragment evaluates options = F_NUMERIC as if -n was used.
I created a separate network namespace (to make sure as little traffic as possible interferes) with a veth pair, then used wireshark there. (If you want to replicate my results and need help with the procedure, see this answer, example 2).
Ping is the most common network administration utility used to test the reachability of a host on an Internet Protocol (IP) network and to measure the round-trip time for messages sent from the originating host to a destination computer.
Ping sends ICMP echo requests to test the connectivity to other hosts. The output shows if the response was received, packets transmitted and received, packet loss, and round-trip time. If a host isn't responding, ping shows 100 percent packet loss.
Specify the ping packet size (in bytes).Default: 32 bytesSize range: 1 to 65507 Traceroute Traceroute traces the path taken by a packet from the source system to the destination system. The output shows all the routers through which data packets pass from the source system to the destination system, maximum hops, and total time taken by the packet to return (measured in milliseconds).
You can use name lookup to query the domain name service for information about domain names and IP addresses. It sends a domain name query packet to a configured domain name system (DNS) server. If you enter a domain name, the server returns the IP address associated with that domain name, and if you enter an IP address, the server returns the domain name associated with that IP address.
Should resolve the name from the IP address if the reverse lookup zone has been set up properly. If the reverse lookup zone does not have an entry for the record, the -a will just ping without a name.
The trouble with "ping" is that it's not strictly a name server lookup tool (like nslookup) - for instance if you ping a hostname, it can be resolved to an IP address by a number of methods: DNS lookup, host file lookup, WINS (god forbid) or NetBIOS broadcast. It can also return a potentially out-dated cached result.
I don't know why, but apparently my SRX can't resolve internet domain names, for example www.juniper.net
I realized this because I created a policy to block some internet pages, but this policy never worked, I had to modify this policy and aggregate the IPv4 of destination page, so I assume that my policy doesn't work because my SRX is not resolving domain names.
You need to provide more details, maybe your full configuration except passwords and public IPs. I have no problem pinging to www.juniper.net from my SRXs. DNS is also 8.8.8.8. Maybe DNS requests are blocked due to some reason in your network?
First question would be does the firewall support dns names instead IP's in its source and destination rule sets? Also enabling host inbound services dns i doubt would work, as the firewall will request a dns lookup from a random port, and the dns server will reply to that random port, look at your session table under self traffic policy. I would suggest you close that port as you open you RE to dns from the internet.
Traceroute, Ping, MTR, and PathPing are network tools or utilities that use the ICMP protocol to perform testing to diagnose issues on a network. Internet Control Message Protocol (ICMP) is an error reporting and diagnostic utility. ICMPs are used by routers, intermediary devices, or hosts to communicate updates or error information to other routers, intermediary devices, or hosts.
Traceroute is a computer network diagnostic tool for displaying the route (path), and measuring transit delays, of packets across an Internet Protocol (IP) network. This section shows how to run Traceroute, and how to interpret the results.
The Traceroute tool is used to map the hops between the end user and the destination server. This can help determine where any issues may lie on the network. The examples below were collected after tracing a route to server 192.168.1.8, over a maximum of 30 hops. They show a good traceroute, then two bad traceroutes; one a failed hop, and one a routing loop.
You can see each step the data takes when it travels to the destination server of 192.168.1.8. These are called hops, and represent a system or router the data passes though. As you can see, hop 7 in this example has not responded, but hop 8 has, meaning that hop 7 is not responding to the request but is handling the packets properly and forwarding traffic to the next hop.
In the good traceroute example earlier, hop 7 was not responding to the request, but had not failed, as it was forwarding traffic to hop 8. The result of a test where one hop isn't responding, and is not forwarding traffic, would look something like this:
This shows the test failing at hop 5, and continuing to fail all the way to hop 30 (the default max hops for the trace route tool) this means that hop 5 is unresponsive and not responding, or forwarding traffic for subsequent hops.
When a routing loop occurs it stops data from reaching the final destination. Unlike the failed hop, the routing loop simply loops data back and forth between two hops. In the example below, a loop has occurred between 192.168.1.4 and 192.168.1.5. Data will pass back and forth from one to the other until the session times out or, in this particular case, the maximum hop limit is reached.
As you can see in this test we dropped two packets but, due to the large sample size, this is negligible and is well within working parameters. If we had a sample size of just four pings this would be a loss of 50% and would not be a true reflection of loss on the circuit.
MTR probes routers on the route path by limiting the number of hops that individual packets may traverse, and listening to responses of their expiry. It will regularly repeat this process, usually once per second, and keep track of the response times of the hops along the path.
This network utility is a more advanced version of the Ping tool, which performs a ping to each hop along the route to the destination (unlike Ping, which just pings from the originating device to the destination device). It is extremely useful in diagnosing packet loss, and can help with diagnosing slow speed faults.
The advantages of PathPing over Ping and Traceroute are that each node is pinged as the result of a single command, and that the behaviour of nodes is studied over an extended time period, rather than the default ping sample of four messages, or default traceroute single route trace. The disadvantage is that it takes a total of 25 seconds per hop to show the PathPing statistics.
A result showing loss from the first hop indicates the likely cause to be the originating end user's router, and would be reflected with the IP address of the router (such as 192.168.0.1). In this instance, check, and if necessary replace, the router, then retest. If the loss is evident from a hop after the originating router (most likely hop 2 onwards), then the issue should be raised to the service provider.
No packets have been dropped on hop 3, but it does have an abnormally high ping response time of 304ms. This could indicate that the hardware on that hop is not performing correctly, and this may be causing high response times and slow speeds. If the hardware on that hop is not performing correctly, you would see high ping times on all subsequent hops, in which case, investigate the hardware on that hop.
As you can see this hop has not responded to any pings sent to it, but has not dropped any pings sent through it. As mentioned in, Understanding ping results, this is due to the server not responding to ICMP ping requests for security or service reasons and does not indicate a problem.
When you see the 0 hop repeated, followed by 0.0.0.0, this means the hop is not responding to the ping correctly. Unfortunately, this is a limitation of the PathPing tool and the way it handles ping responses.
You will want to ensure that you are not using a service route though, as the DNS requests are all sent using that service route. The service routes are configured at Device > Setup > Services > Service Route Configuration. If you do have a service route set, your ping and all DNS lookups where the firewall initiates connections (such as updates.paloaltonetworks.com) will use that route.
If you HTTPS to the firewall and create an Address as an FQDN instead of an IP, there is a clickable RESOLVE link next to where you place the DNS name. That will resolve and list all the IP addresses it pulled from DNS. This is better than a PING test as PING will only show the first of many IPs. Using the FQDN address object you can see the full list.
So I am trying to Purge IPs from tool that we use. Before I can purge the assets we need to make sure the host is not pingable and not in DNS. I am new to PS and cant seem to wrap my head around on doing this. Any help is greatly appreciated. I have been doing this as a manual process by pinging the list of IPs and hostnames and doing a nslookup in cmd prompt before selecting the IPs that are needing to be removed. I have about 13k IPs left to do.
Update:I want to implement this portion into it. Where In cell A it will have the IPcell B will let me know if it is up or down. And Cell D will let me know if it is DNS aswell. Below is the script I got for pinging and checking if up or down and checking AD to see if the hostname is still in AD. I want it similar to this.. Please excuse my english
Members of administrators' groups are a priority target. By misconfiguring their protection, the password of the account can be retrieved by an attacker, or it can leverage internal mechanisms of the AD such as authentication to act on its behalf.
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