Can you assign different DNS servers to different network interfaces?
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I am trying to have my eth1 use 10.50.1.11 and 10.50.1.12 dns servers whilst my eth0 interface uses 8.8.8.8 and 8.8.4.4 dns servers.
I am running centos 7 vms within xenserver 6.5. eth1 is a closed-circuit vlan, whilst eth0 is the public network. The problem im having is that my centos
client automatically picks which dns server it uses based upon which interface comes up first. I know that when you define dns servers in
/etc/network-scripts/ifcfg-eth0 or /etc/network-scripts/ifcfg-eth1, it prints it out inside of /etc/resolv.conf, but i cant find a workaround for this.
Does anyone know if you can assign different DNS servers to different network interfaces?
centos networking dns network-interface xen
edited Mar 5 at 17:30
Rui F Ribeiro
41.8k1483142
asked Mar 5 at 17:11
DodeDode
32
add a comment |
I am trying to have my eth1 use 10.50.1.11 and 10.50.1.12 dns servers whilst my eth0 interface uses 8.8.8.8 and 8.8.4.4 dns servers.
I am running centos 7 vms within xenserver 6.5. eth1 is a closed-circuit vlan, whilst eth0 is the public network. The problem im having is that my centos
client automatically picks which dns server it uses based upon which interface comes up first. I know that when you define dns servers in
/etc/network-scripts/ifcfg-eth0 or /etc/network-scripts/ifcfg-eth1, it prints it out inside of /etc/resolv.conf, but i cant find a workaround for this.
Does anyone know if you can assign different DNS servers to different network interfaces?
centos networking dns network-interface xen
edited Mar 5 at 17:30
Rui F Ribeiro
41.8k1483142
asked Mar 5 at 17:11
DodeDode
32
3
DNS does not work as you think it works. It is global to the system, not based on interface.
– Rui F Ribeiro
Mar 5 at 17:31
1
This sounds like an XY problem. Consider asking a separate question where you explain what exactly is the end result that you want to achieve. This general question is still perfectly valid and interesting for people wondering how DNS resolution works.
– TooTea
Mar 5 at 18:05
1
You can use network namespaces, puteth0andeth1into different namespaces (or one in the main namespace, one in a new namespace). Network namespace allows different versions ofresolv.confin/etc/netns/<namespace_name>/resolv.conf, at least for sufficiently modern applications that pay attention to that.
– dirkt
Mar 6 at 11:08
add a comment |
I am trying to have my eth1 use 10.50.1.11 and 10.50.1.12 dns servers whilst my eth0 interface uses 8.8.8.8 and 8.8.4.4 dns servers.
I am running centos 7 vms within xenserver 6.5. eth1 is a closed-circuit vlan, whilst eth0 is the public network. The problem im having is that my centos
client automatically picks which dns server it uses based upon which interface comes up first. I know that when you define dns servers in
/etc/network-scripts/ifcfg-eth0 or /etc/network-scripts/ifcfg-eth1, it prints it out inside of /etc/resolv.conf, but i cant find a workaround for this.
Does anyone know if you can assign different DNS servers to different network interfaces?
centos networking dns network-interface xen
edited Mar 5 at 17:30
Rui F Ribeiro
41.8k1483142
asked Mar 5 at 17:11
DodeDode
32
I am trying to have my eth1 use 10.50.1.11 and 10.50.1.12 dns servers whilst my eth0 interface uses 8.8.8.8 and 8.8.4.4 dns servers.
I am running centos 7 vms within xenserver 6.5. eth1 is a closed-circuit vlan, whilst eth0 is the public network. The problem im having is that my centos
client automatically picks which dns server it uses based upon which interface comes up first. I know that when you define dns servers in
/etc/network-scripts/ifcfg-eth0 or /etc/network-scripts/ifcfg-eth1, it prints it out inside of /etc/resolv.conf, but i cant find a workaround for this.
Does anyone know if you can assign different DNS servers to different network interfaces?
centos networking dns network-interface xen
centos networking dns network-interface xen
edited Mar 5 at 17:30
Rui F Ribeiro
41.8k1483142
asked Mar 5 at 17:11
DodeDode
32
edited Mar 5 at 17:30
Rui F Ribeiro
41.8k1483142
asked Mar 5 at 17:11
DodeDode
32
edited Mar 5 at 17:30
Rui F Ribeiro
41.8k1483142
edited Mar 5 at 17:30
Rui F Ribeiro
41.8k1483142
edited Mar 5 at 17:30
Rui F Ribeiro
41.8k1483142
41.8k1483142
asked Mar 5 at 17:11
DodeDode
32
asked Mar 5 at 17:11
DodeDode
32
asked Mar 5 at 17:11
DodeDode
32
32
3
DNS does not work as you think it works. It is global to the system, not based on interface.
– Rui F Ribeiro
Mar 5 at 17:31
1
This sounds like an XY problem. Consider asking a separate question where you explain what exactly is the end result that you want to achieve. This general question is still perfectly valid and interesting for people wondering how DNS resolution works.
– TooTea
Mar 5 at 18:05
1
You can use network namespaces, puteth0andeth1into different namespaces (or one in the main namespace, one in a new namespace). Network namespace allows different versions ofresolv.confin/etc/netns/<namespace_name>/resolv.conf, at least for sufficiently modern applications that pay attention to that.
– dirkt
Mar 6 at 11:08
add a comment |
3
DNS does not work as you think it works. It is global to the system, not based on interface.
– Rui F Ribeiro
Mar 5 at 17:31
1
This sounds like an XY problem. Consider asking a separate question where you explain what exactly is the end result that you want to achieve. This general question is still perfectly valid and interesting for people wondering how DNS resolution works.
– TooTea
Mar 5 at 18:05
1
You can use network namespaces, puteth0andeth1into different namespaces (or one in the main namespace, one in a new namespace). Network namespace allows different versions ofresolv.confin/etc/netns/<namespace_name>/resolv.conf, at least for sufficiently modern applications that pay attention to that.
– dirkt
Mar 6 at 11:08
3
3
DNS does not work as you think it works. It is global to the system, not based on interface.
– Rui F Ribeiro
Mar 5 at 17:31
DNS does not work as you think it works. It is global to the system, not based on interface.
– Rui F Ribeiro
Mar 5 at 17:31
1
1
This sounds like an XY problem. Consider asking a separate question where you explain what exactly is the end result that you want to achieve. This general question is still perfectly valid and interesting for people wondering how DNS resolution works.
– TooTea
Mar 5 at 18:05
This sounds like an XY problem. Consider asking a separate question where you explain what exactly is the end result that you want to achieve. This general question is still perfectly valid and interesting for people wondering how DNS resolution works.
– TooTea
Mar 5 at 18:05
1
1
You can use network namespaces, put
eth0 and eth1 into different namespaces (or one in the main namespace, one in a new namespace). Network namespace allows different versions of resolv.conf in /etc/netns/<namespace_name>/resolv.conf, at least for sufficiently modern applications that pay attention to that.– dirkt
Mar 6 at 11:08
You can use network namespaces, put
eth0 and eth1 into different namespaces (or one in the main namespace, one in a new namespace). Network namespace allows different versions of resolv.conf in /etc/netns/<namespace_name>/resolv.conf, at least for sufficiently modern applications that pay attention to that.– dirkt
Mar 6 at 11:08
add a comment |
1 Answer
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No, that simply can't be done due to the way address resolution works.
When a process on the machine wants to connect to, say, example.com, it first calls a library routine like getaddrinfo or gethostbyname. The purpose of these routines is to translate the DNS name to an IP address. So they look into /etc/resolv.conf, read the IP address of a DNS server, send a DNS query packet to that server, receive the reply and return the resulting IP address to the caller.
At that point, the process takes the resolved IP address and passes it to a system call such as connect. This is where the kernel steps in, looks into its routing table and figures out which interface to use to connect to that address.
So in short, DNS settings simply cannot depend on the interface used for communication, because the choice of that interface itself depends on the DNS settings.
answered Mar 5 at 18:00
TooTeaTooTea
784211
add a comment |
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No, that simply can't be done due to the way address resolution works.
When a process on the machine wants to connect to, say, example.com, it first calls a library routine like getaddrinfo or gethostbyname. The purpose of these routines is to translate the DNS name to an IP address. So they look into /etc/resolv.conf, read the IP address of a DNS server, send a DNS query packet to that server, receive the reply and return the resulting IP address to the caller.
At that point, the process takes the resolved IP address and passes it to a system call such as connect. This is where the kernel steps in, looks into its routing table and figures out which interface to use to connect to that address.
So in short, DNS settings simply cannot depend on the interface used for communication, because the choice of that interface itself depends on the DNS settings.
answered Mar 5 at 18:00
TooTeaTooTea
784211
add a comment |
No, that simply can't be done due to the way address resolution works.
When a process on the machine wants to connect to, say, example.com, it first calls a library routine like getaddrinfo or gethostbyname. The purpose of these routines is to translate the DNS name to an IP address. So they look into /etc/resolv.conf, read the IP address of a DNS server, send a DNS query packet to that server, receive the reply and return the resulting IP address to the caller.
At that point, the process takes the resolved IP address and passes it to a system call such as connect. This is where the kernel steps in, looks into its routing table and figures out which interface to use to connect to that address.
So in short, DNS settings simply cannot depend on the interface used for communication, because the choice of that interface itself depends on the DNS settings.
answered Mar 5 at 18:00
TooTeaTooTea
784211
add a comment |
No, that simply can't be done due to the way address resolution works.
When a process on the machine wants to connect to, say, example.com, it first calls a library routine like getaddrinfo or gethostbyname. The purpose of these routines is to translate the DNS name to an IP address. So they look into /etc/resolv.conf, read the IP address of a DNS server, send a DNS query packet to that server, receive the reply and return the resulting IP address to the caller.
At that point, the process takes the resolved IP address and passes it to a system call such as connect. This is where the kernel steps in, looks into its routing table and figures out which interface to use to connect to that address.
So in short, DNS settings simply cannot depend on the interface used for communication, because the choice of that interface itself depends on the DNS settings.
answered Mar 5 at 18:00
TooTeaTooTea
784211
No, that simply can't be done due to the way address resolution works.
When a process on the machine wants to connect to, say, example.com, it first calls a library routine like getaddrinfo or gethostbyname. The purpose of these routines is to translate the DNS name to an IP address. So they look into /etc/resolv.conf, read the IP address of a DNS server, send a DNS query packet to that server, receive the reply and return the resulting IP address to the caller.
At that point, the process takes the resolved IP address and passes it to a system call such as connect. This is where the kernel steps in, looks into its routing table and figures out which interface to use to connect to that address.
So in short, DNS settings simply cannot depend on the interface used for communication, because the choice of that interface itself depends on the DNS settings.
answered Mar 5 at 18:00
TooTeaTooTea
784211
answered Mar 5 at 18:00
TooTeaTooTea
784211
answered Mar 5 at 18:00
TooTeaTooTea
784211
answered Mar 5 at 18:00
TooTeaTooTea
784211
784211
add a comment |
add a comment |
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3
DNS does not work as you think it works. It is global to the system, not based on interface.
– Rui F Ribeiro
Mar 5 at 17:31
1
This sounds like an XY problem. Consider asking a separate question where you explain what exactly is the end result that you want to achieve. This general question is still perfectly valid and interesting for people wondering how DNS resolution works.
– TooTea
Mar 5 at 18:05
1
You can use network namespaces, put
eth0andeth1into different namespaces (or one in the main namespace, one in a new namespace). Network namespace allows different versions ofresolv.confin/etc/netns/<namespace_name>/resolv.conf, at least for sufficiently modern applications that pay attention to that.– dirkt
Mar 6 at 11:08