Pings & DNS lookups failing from 4th router in chain

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AbeFroman
DD-WRT Novice


Joined: 10 Jan 2017
Posts: 6

PostPosted: Tue Jan 10, 2017 17:57    Post subject: Pings & DNS lookups failing from 4th router in chain Reply with quote
I have four routers chained together.
Router 1 (Linksys 300N) is connected to a DSL modem and also acts as an AP. It is the default gateway for the network (192.168.1.1).

The DSL modem provides two DNS server addresses:
DNS Servers . . . : 192.168.0.1 & 205.171.3.65

Router 2 (Linksys 150N) is client-bridged to router 1.
Router 3 (Linksys 150N) is directly cabled to router 2 and is client-bridged to router 4.

Router 4 (Linksys 300N) acts as an AP with an SSID different from router 1.

All routers, except router 1, are running DD-WRT.

I can ping router 1 (192.168.1.1) from a PC cabled to router 4. I cannot ping the DSL modem (192.168.0.1) from the same PC and cannot lookup DNS names from that PC.

An "ipconfig/all" from the PC connected to router 4 shows

Windows IP Configuration

Host Name . . . . . . . . . . . . : 9500-XYLON
Primary Dns Suffix . . . . . . . :
Node Type . . . . . . . . . . . . : Unknown
IP Routing Enabled. . . . . . . . : Yes
WINS Proxy Enabled. . . . . . . . : No
DNS Suffix Search List. . . . . . : Home

Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix . : Home
Description . . . . . . . . . . . : Broadcom NetXtreme 57xx Gigabit Controller
Physical Address. . . . . . . . . : 00-14-22-C4-28-82
Dhcp Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IP Address. . . . . . . . . . . . : 192.168.1.103
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.1.1
DHCP Server . . . . . . . . . . . : 192.168.1.1
DNS Servers . . . . . . . . . . . : 192.168.0.1
205.171.3.65
As you can see, the PC has obtained an IP and default gateway address and both of the network DNS server addresses from router 1.

What is blocking DNS lookups and pings to the DSL modem from the PC connected to router 4?
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egc
DD-WRT Guru


Joined: 18 Mar 2014
Posts: 12837
Location: Netherlands

PostPosted: Tue Jan 10, 2017 19:52    Post subject: Reply with quote
If I understand correctly your DSL modem is not in bridge mode, it is on a separate network: 192.168.0.0

Router one is acting as gateway and the WAN port of router one is connected to the DSL modem.
This WAN connection type must be Automatic, router IP 192.168.1.1 with netmask 255.255.255.0
Leave everything else 0.0.0.0
This will result in a DNS server of 192.168.1.1 and NOT 192.168.0.1

If you have a look at the Status/WAN page of router one there should be the IP address of the WAN port which is something llike 192.168.0.x and corresponding netmask and DNS server.

Edit: all other routers should have dhcp server disabled

This should give you internet access (I hope)

If this works we can take the next step, which is linking subnets Smile

There is of course an alternative and that is to let the DSL modem do all the hard work and have one subnet that is the subnet of the DSL modem 192.168.0.0

_________________
Routers:Netgear R7000, R6400v1, R6400v2, EA6900 (XvortexCFE), E2000, E1200v1, WRT54GS v1.
Install guide R6400v2, R6700v3,XR300:https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=316399
Install guide R7800/XR500: https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=320614
Forum Guide Lines (important read):https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=324087
AbeFroman
DD-WRT Novice


Joined: 10 Jan 2017
Posts: 6

PostPosted: Tue Jan 10, 2017 22:59    Post subject: Reply with quote
Here is the info from the router connected to the DSL modem.

Connection Type: Automatic Configuration DHCP

Internet IP Address: 192.168.0.2
Subnet Mask: 255.255.255.0
Default Gateway: 192.168.0.1
DNS1: 192.168.0.1
DNS2: 205.171.3.65

Address 192.168.0.1 seems to be on the DSL modem.
Address 192.168.0.2 seems to be on the router interface connected to the modem.

Tracing route to 192.168.0.2
1 1 ms <1 ms <1 ms 192.168.0.2
Trace complete.

Tracing route to 192.168.0.1
1 3 ms <1 ms <1 ms 192.168.1.1
2 2 ms <1 ms <1 ms 192.168.0.1
Trace complete.
AbeFroman
DD-WRT Novice


Joined: 10 Jan 2017
Posts: 6

PostPosted: Tue Jan 10, 2017 23:04    Post subject: Source of tracert commends Reply with quote
BTW, the tracert commands were executed on a PC that is a wireless client of the 300N via a PCM card.
AbeFroman
DD-WRT Novice


Joined: 10 Jan 2017
Posts: 6

PostPosted: Tue Jan 10, 2017 23:17    Post subject: Pings & DNS lookups failing from 4th router in chain Reply with quote
DNS lookups work if I connect a PC to any of the other routers in the chain but router 4.

The problem occurs just when making that final jump.

I hope I'm still correct in saying that.
I've checked this previously but will check again
right now.
AbeFroman
DD-WRT Novice


Joined: 10 Jan 2017
Posts: 6

PostPosted: Tue Jan 10, 2017 23:20    Post subject: Reply with quote
Yes, it is as I said in the previous reply.
I moved the PC (cable) from router 4 to router 3 and everything works OK.
AbeFroman
DD-WRT Novice


Joined: 10 Jan 2017
Posts: 6

PostPosted: Wed Jan 11, 2017 2:41    Post subject: Reply with quote
What's odd about this is if I reverse the functions of the 3rd and 4th routers everything works. That is, I make router 3 an access point and router 4 is client-bridged to router 3.
egc
DD-WRT Guru


Joined: 18 Mar 2014
Posts: 12837
Location: Netherlands

PostPosted: Wed Jan 11, 2017 8:45    Post subject: Reply with quote
Be sure to disable DHCP server on routers 2,3 and 4 and also disable DNS masq from the services tab.
Do not use the WAN port if you have wired connections between the routers.
This is to create one subnet for routers 1,2,3,4 where only router 1 has the DHCP server at 192.168.1.1 with DNS server and default gateway at 192.168.1.1.

For linking the routers have a look at: http://www.dd-wrt.com/wiki/index.php/Linking_Routers

_________________
Routers:Netgear R7000, R6400v1, R6400v2, EA6900 (XvortexCFE), E2000, E1200v1, WRT54GS v1.
Install guide R6400v2, R6700v3,XR300:https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=316399
Install guide R7800/XR500: https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=320614
Forum Guide Lines (important read):https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=324087
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