Hot answers tagged ip
61
The TTL get decremented when it pass through a router. This makes sure that if the packet is traveling around in circles it will eventually die.
The TTL field of an IP v4 packet is an 8-bit field (255 decimal). So setting it high at the start it isn't a big deal since it can't actually be that large in a well-formed packet (Although, some things might ...
16
The TTL on packets keeps routing sane, basically. If a packet were to have a very large TTL and was caught in a circular route for some reason, it could cause a ton of traffic (called a "packet storm") and interfere with normal operations. Too low TTL would result in loss of connectivity as you'd lose the packet before it reached the destination.
7
To get a clear answer, you'll need to properly define 'me' and 'not the whole world', as well as how you want to access. From reading the question 'prevent apache remote access'.. listening on loopback (127.0.0.1) only (which means it's not reachable via the network) is EXACTLY what you did.
Likely you'll find all the documentation you need to configure ...
5
There's no end of tools around for testing how DNS settings are seen from the outside world. I've used DNSStuff in the past, but there are lots out there. The biggest test of course is whether or not you get complaints from customers about the site being down, and this can still happen because of cached info on their local DNS or other similar issues ...
4
Ok, I figured it out:
Add-VMNetworkAdapterAcl -VMName $vmName -LocalIPAddress $vmIP -Direction Both -Action Allow
Add-VMNetworkAdapterAcl -VMName $vmName -LocalIPAddress Any -Direction Both -Action Deny
This will limit a VM guest to use only a specific IP address. If he changes the IP, he will not be able to reach the internet or any other local IP ...
4
The router is correct, because with that subnet mask those addresses do overlap.
192.168.2.1/21, which is what your command tries to configure, is part of a subnet that includes everything from 192.168.1.1 through 192.168.7.255. What you mean to configure is 192.168.2.1/24 which is a mask of 255.255.255.0.
You may find it useful to use a subnet calculator ...
4
There's one point which the answers appear to have missed but which would be purely academic (because of how many hops seem to be required on the internet): if a packet would normally fail to reach it's destination because of an expiring TTL, then increasing it would allow the packet to reach it's destination but would not affect packets being returned and ...
3
SRV records can be used by clients to lookup the location of a service (by hostname and port; as well as some other details). Any service can be looked up this way.
For a web server it would be _http._tcp.example.com.
I don't know of any web browser that looks up SRV records however, so setting it would be pretty useless. Minecraft clients specifically ...
3
arping can help you in disvovering IP clashes. Just send an arping to the IP:
# arping 172.16.10.1
ARPING 172.16.10.1 from 172.16.10.204 eth0
Unicast reply from 172.16.10.1 [00:10:DB:FC:11:00] 0.982ms
Unicast reply from 172.16.10.1 [00:10:DB:FC:11:00] 0.966ms
Unicast reply from 172.16.10.1 [00:10:DB:FC:11:00] 0.975ms
Unicast reply from 172.16.10.1 ...
2
An FQDN is the full domain name localized into the DNS hierarchy, for instance mysql-backend.example.lan.
An IP address is not a FQDN.
If your software requires you a FQDN please evaluate to add a record to your DNS server cache or to /etc/hosts:
192.168.9.200 mysql-backend.example.lan mysql-backend
1
It looks like your DNS entries are not complete. You do not have an A record with an IP address.
Currently, its:
$ dig spdserver.com
; <<>> DiG 9.4.1 <<>> spdserver.com
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 1125
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, ...
1
I like dig:
$ dig any example.com
; <<>> DiG 9.9.2-rl.028.23-P2-RedHat-9.9.2-10.P2.fc18 <<>> any example.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 52655
;; flags: qr rd ra; QUERY: 1, ANSWER: 7, AUTHORITY: 2, ADDITIONAL: 0
;; QUESTION SECTION:
;example.com. ...
1
Nick W's answer is correct.
However well you understand the theory of these CIDR network specifications, working the numbers out by hand is tedious and error prone. I recommend a tool called ipcalc which is available in the software repositories associated with many of the major Free *nix distributions. It's good for getting the calculations right, and ...
1
Sockets are uniquely identified by the combination of (source ip, source port, destination ip, destination port), so your A scenario is correct.
Take a minute and think through the ramifications if B were the case. Firewalling would be near impossible if the destination port were constantly changing - there would need to be constant communication between ...
1
It's SO much easier than you think.
The server's listening on say port 80, it gets a packet in from 20.xx so knows that 20.xx wants something so goes and does it and send it back to 20.xx. Then 30.xx comes and asks on port 80 so it responds back directly to 30.xx.
That's it, nothing much more complex.
It's a bit like if you're on the phone and you can ...
1
If the load balancer is inserting the client IP address in a header called ClientIP, mod_proxy should pass that on to the Tomcat sever without any special configuration. Try configuring the Tomcat RemoteIpValve to look for ClientIP instead of X-Forwarded-For. e.g.
<Valve className="org.apache.catalina.valves.RemoteIpValve"
...
1
You have a /21 mask (255.255.255.248)
The first interface (192.168.1.1/21) is then in this subnet:
Address: 192.168.1.1 11000000.10101000.00000 001.00000001
Netmask: 255.255.248.0 = 21 11111111.11111111.11111 000.00000000
Wildcard: 0.0.7.255 00000000.00000000.00000 111.11111111
Network: 192.168.0.0/21 ...
1
Try arp-scan:
http://linux.die.net/man/1/arp-scan
With the option --localnet you can scan your whole subnet with it.
In order to get this checked automatically, you could create a cronjob that does something like
arp-scan --localnet|tail -n +3|head -n -3|awk {'print $1'}|uniq -c
output on my box:
1 172.16.10.1
1 172.16.10.2
1 172.16.10.27
1 ...
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