3com MSR 20-20 참조 매뉴얼

If a PC is connected to the device using PPP, you can use the winipcfg command 
or the ipconfig/all command to view its DNS server address assigned by the 
device.

A sysname device can provide a primary DNS server address and a secondary DNS 
server address.

# Configure the local device to assign primary DNS server address 100.1.1.1, and 
secondary DNS server address 100.1.1.2 to its peer.

<Sysname> system-view

[Sysname] interface serial 1/0

[Sysname-Serial1/0] ppp ipcp dns 100.1.1.1 100.1.1.2 

Interface view

None

Use the ppp ipcp dns admit-any command to configure the device to passively 
accept the DNS server address assigned by the peer, even without sending a DNS 
request.

Use the undo ppp ipcp dns admit-any command to disable this function.

By default, a device does not passively accept DNS server address assigned by the 
peer.

When a device is connected to another device (for example, a network access 
server of a service provider) using PPP, the device can be configured to accept the 
DNS server address allocated by the peer to resolute the domain name.

# Set the interface Serial 1/0 of the local device to accept DNS server address 
allocated by the peer.

<Sysname> system-view

[Sysname] interface serial 1/0

[Sysname-Serial1/0] ppp ipcp dns admit-any 

Interface view