In our company network we have the following setup:
a Debian server with a DHCP server (isc-dhcp-server 4.3.1, backported on Debian 7.8)
which serves client requests from an IP pool
two Windows DCs for DNS (Windows Server 2008 R2)
The DHCP server is configured to register client address records dynamically to the DNS server. Our config:
ddns-updates on;
ddns-update-style standard;
update-conflict-detection false;
allow client-updates;
ddns-domainname "local.domain.com";
ddns-rev-domainname "in-addr.arpa.";
update-static-leases true;
default-lease-time 7200;
max-lease-time 7200;
authoritative;
[...]
Whenever a client gets a new IP from the DHCP, the DNS registration works perfectly.
However, these "dynamic" DNS records expire after some time (a few weeks)...
How can the DHCP be configured to refresh the DNS records after a given time interval?
Currently, the DNS is only updated once when a client gets a new
IP address (or after a DHCP RELEASE/DHCP REQUEST).
I believe you may need to disable update-optimization i.e. by including a line of the form:
update-optimization false;
That will cause the server to do DDNS updates on every renewal, rather than the default of when something changes.
Related
I'm attempting to set up a STUN server using STUN server for Node.js:
https://github.com/enobufs/stun
The readme has the following guidance:
Place a config file named as node-stun.ini in
your current directory. The config file should look like following.
(These local loopback addresses should be routable public IP addresses
in the real settings, of course)
[primary] host = 127.0.0.1
[secondary] host = 127.0.0.2
Does anyone know what the primary and secondary IPs should be? Should the primary be the IP address of my STUN server machine? What should the secondary be?
Could I set them as localhost and route requests to the server with nginx?
Finally, why does the software need to refer to these IP addresses?
Technically, STUN requires two unique public IP addresses on the server. But most client implementations only need one and don't use the alternate/secondary address. And the server code needs to know what these addresses are for two reasons:
So that the server knows which address to bind the sockets to. (It would need the local ip addresses for each)
So that the server can advertise the alternate IP address when a binding request hits the primary IP. (It needs to know the public IP addresses of the host if its behind a NAT with port forwarding).
If you don't have a secondary IP address to offer, then give in any address that allows the server to run. This will break STUN behavior and filtering tests, but rarely do clients need this.
I have been recently exploring the DNS service and how things work. From my understanding if the browser does not know a certain URL that is typed by the user (ex. maps.google.com) then the DNS flow will be the following:
Browser checks its cache => Browser checks with the OS resolver software on the device (possibly checks the host.txt file that exists on the machine if it is Windows) => Operating system contacts the ISP DNS server => ISP DNS server checks cache and then resolver software from ISP DNS server reaches a DNS Root server IP address directly (root server IPs are hard-coded in the ISP resolver) => Root server directs resolver to TLD servers (.com in our example) => TLD servers sent the resolver to Authoritative servers for the domain we asked (google.com) => Authoritative server gives us the Ip address we look for (maps.google.com)
I am experimenting with the nslookup command in Windows 10. I do the following:
C:\Users\me>nslookup
Default Server: UnKnown
Address: "Here I get an Ip6 address"
>root
Default Server: A.ROOT-SERVERS.NET
Addresses: 2001:503:ba3e::2:30
198.41.0.4
Above we can see one of the root DNS servers of Verizon which is used to provide the DNS service to the users on the Internet.
My questions is:
The information returned from the root comamnd in the nslookup mode, where are they coming from?
Are these information from the cache of my PC or they are information that are saved on the DNS server that my pc is contacting to get the DNS service?
Ok, well the 13 root a servers are the master controllers of the entire web. They are too busy to be bothered with every request so they have replicators--hundreds of other servers that have already asked and answered your question--and got a resolved website. They then get to answer the question on behalf of the 13 root servers--for a set amount of time.
I start a capture with no other applications running on my machine other than chrome and Wireshark, and then I start a capture with Wireshark. And go to a website for about 20 seconds. How can I look at the DNS queries all sent in the capture time?
So for any given website, I need to find the
DNS resolved ip address
DNS server ip (I believe this is the destination ip)
DNS server port
Just enter the word dns in the filter field... simple as that
see more here
I've got a customer where the router needs to be replaced with a Cisco router.
The current router is a linux machine with webmin installed on it.
There's a BIND DNS server with multiple zones.
There's a zone called companyname.be with entries name-ip (address records).
There's also a zone called 192.9.200 (which is the local subnet) with entries address-name (reverse address records).
This configuration can be seen below:
I'm not sure why they need this but someone at the customer's company told me that it's necessary.
In the end the goal is to be able to ping by using a name rather than an IP.
Does someone know how to configure this in Cisco IOS?
I've been searching this for a while now but all I came up with is this link: http://www.firewall.cx/cisco-technical-knowledgebase/cisco-routers/257-cisco-router-dns-server.html
I tried it but this only seems to create a host table on the router itself.
That hosttable is not used by the DNS.
(Can ping to domain name from router CLI but cannot ping to a domain name from a PC with that router as default gateway.)
I've already found the answer here: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipaddr_dns/configuration/15-sy/dns-15-sy-book/Configuring-DNS.html#GUID-E4A67061-354E-4847-8F56-9A88446C7D30
R1#conf t
R1(config)#ip domain companyname.be
R1(config)#ip name-server 8.8.8.8
R1(config)#ip dns server
R1(config)#ip host computername1.companyname.be
And for the DHCP server to send the DNS server to DHCP clients:
R1(config)#ip dhcp pool pool_name
R1(dhcp-config)#dns-server ip_address_of_router
Now any host can ping computername1.companyname.be.
I have a question in Cisco Packet Tracer.
I have a Router and a Dns server and my Config from Dns is blocked. How can I start the DNS server using the Router?
ip dns server ... doesn't work
Thank you
Unfortunately Cisco Packet Tracer does not support command "ip dns server" hence you can not use Router like Dns server.
All supported commands you can see in Program_Root_Dir\help\default\index.html or push a question mark in the program.
First, you need to attach "WIC 1ENET" in Router to connect it with DNS server
Second, you need an IP address in DNS server For example (192.168.3.2)
Third, enter Gateway like this (192.168.3.1), and DNS server (192.168.3.2)
fourth, Enter the DNS server and go to Services and enter Name and address like this Figure, and then ADD.
Finally, Go to the end Host (PC), then Desktop and then IP Configuration, and Enter the DNS server (192.168.3.2).
I hope that's helpful for you to understand and make it work.
You need enable any routing protocol and add the network where is the DNS Server.