Different routers can't access the same sites.

Z

zoot

Active Member
Joined
May 30, 2005
Messages
90
Reaction score
0
Location
Cape Town (CBD)
Hi everyone

I recently bought a Tenda D820R ADSL router, which can access many sites, but can't access some specific sites. On replacing the Tenda router with a Netgear DG834G, as a test, to see if the router might be the cause, it was! I could access all the sites via the Netgear router, but not the Tenda router. I find this very strange, that most sites are accessible, bar one, or two.

Setup 1:

Office PCs --- ethernet --- Tenda ADSL router --- ADSL splitter -- Telkom line

Can access most sites, but can't access http://www.hootsuite.com, http://yahoo.com and some others.

Setup 2:

Office PCs --- WiFi --- Netgear ADSL router --- ADSL splitter -- Telkom line

Can access the problematic sites of Setup 1.

Both routers have their respective MTU settings at 1492.

Could this problem have something to do with the difference in MTU settings of the ethernet port on the Tenda router versus the WiFi interface of the Netgear router? Surely not? I don't have sufficient low-level network knowledge in terms of MTU settings and how packets might be altered between source and destination, to know the answer.

Any ideas as to why this strange behaviour might be occurring?
 
zoot said:
Hi everyone

I recently bought a Tenda D820R ADSL router, which can access many sites, but can't access some specific sites. On replacing the Tenda router with a Netgear DG834G, as a test, to see if the router might be the cause, it was! I could access all the sites via the Netgear router, but not the Tenda router. I find this very strange, that most sites are accessible, bar one, or two.

Setup 1:

Office PCs --- ethernet --- Tenda ADSL router --- ADSL splitter -- Telkom line

Can access most sites, but can't access http://www.hootsuite.com, http://yahoo.com and some others.

Setup 2:

Office PCs --- WiFi --- Netgear ADSL router --- ADSL splitter -- Telkom line

Can access the problematic sites of Setup 1.

Both routers have their respective MTU settings at 1492.

Could this problem have something to do with the difference in MTU settings of the ethernet port on the Tenda router versus the WiFi interface of the Netgear router? Surely not? I don't have sufficient low-level network knowledge in terms of MTU settings and how packets might be altered between source and destination, to know the answer.

Any ideas as to why this strange behaviour might be occurring?
Click to expand...

Stick with the netgear and send the "Tenda" (whatever the **** that is) to it's grave.

Most likely the firewall on the router is what is blocking something
 
The first thing to do is identify whether or not it is a DNS issue.
Run nslookup on both sites from both routers and check for differences in the output.
 
twhitehead said:
Most likely the firewall on the router is what is blocking something
Click to expand...

Both routers neither have specific site blocking rules, nor protocol specific QoS setup.

twhitehead said:
The first thing to do is identify whether or not it is a DNS issue.
Run nslookup on both sites from both routers and check for differences in the output.
Click to expand...

DNS queries work perfectly on both. Using one Google DNS cache server and one OpenDNS cache server.
 
Have you tried the Tenda router again?

Most likely it was just a network error further upstream OR a DNS issue.
 
What happens if you go to the ip address in your browser rather than the URL?

Can you ping them from both routers?

I found that if I ping yahoo, it uses the IPv6 address. Maybe one of your routers has issues with IPv6.
I run my own DNS server in order to route Google via a telkom account. However my DNS server does not do IPv6. It cannot look up www.yahoo.com for some reason. An nslookup using Googles DNS, returns both IPv6 and IPv4 addresses, but the IPv6 ones come first.
 
I tried to download information on the Tenda router as I have not heard of that model before but the spec sheet kept timing out.
Is it a new router that you have bought?
Have you also tried Pada's suggestion as well?
 
Firstly, thanks to everyone for contributing to trying to resolve this.

Pada said:
Have you tried the Tenda router again?
Click to expand...

Yes, no change.

twhitehead said:
What happens if you go to the ip address in your browser rather than the URL?
Click to expand...

Nothing. This is not a DNS issue. I've tried various DNS cache settings, from auto, to fixed (Google, OpenDNS) and the IPs of all the "problematic sites" are returned. The connections are initiated, but responses from the sites don't return, so web browsing, ICMP based tools like traceroute indicate packet loss etc.

I am convinced this has something to do with the more subtle ADSL/network layer settings.

Here are the details reported by the Tenda router (The options were all defaults based on the S.Africa settings):

ATM PVC Configuration

VPI: 8
VCI: 35

Service Category:

- UBR without PCR (selected)
- UBR with PCR
- CBR
- Non Realtime VBR
- Realtime VBR

Connection Type

PPPoE

Encapsulation mode

- LLC/SNAP-BRIDGING (selected)
- VC/MUX

MTU

1492

Advanced DSL Settings

Modulation (check-boxes)

[x] G.Dmt
[x] G.lite
[x] T1.413
[x] ADSL2
[x] AnnexL
[x] ADSL2+
[x] AnnexM

Either/or radio button selection:

(o) Inner pair
( ) Outer pair

Capability:

[x] Bitswap enable (checked)
[ ] SRA enable

Test mode (radio buttons):

(o) Normal
( ) Reverb
( ) Medley
( ) No retrain
( ) L3

Then, there's a screen with "Tone selection" with all "upstream tones" and all "downstream tones" selected.
 
Firstly, thanks to everyone for contributing to trying to resolve this.

Pada said:
Have you tried the Tenda router again?
Click to expand...

Yes, no change.

twhitehead said:
What happens if you go to the ip address in your browser rather than the URL?
Click to expand...

Nothing. This is not a DNS issue. I've tried various DNS cache settings, from auto, to fixed (Google, OpenDNS) and the IPs of all the "problematic sites" are returned. The connections are initiated, but responses from the sites don't return, so web browsing, ICMP based tools like traceroute indicate packet loss etc.

I am convinced this has something to do with the more subtle ADSL/network layer settings.

Here are the details reported by the Tenda router (The options were all defaults based on the S.Africa settings):

ATM PVC Configuration

VPI: 8
VCI: 35

Service Category:

- UBR without PCR (selected)
- UBR with PCR
- CBR
- Non Realtime VBR
- Realtime VBR

Connection Type

PPPoE

Encapsulation mode

- LLC/SNAP-BRIDGING (selected)
- VC/MUX

MTU

1492

Advanced DSL Settings

Modulation (check-boxes)

[x] G.Dmt
[x] G.lite
[x] T1.413
[x] ADSL2
[x] AnnexL
[x] ADSL2+
[x] AnnexM

Either/or radio button selection:

(o) Inner pair
( ) Outer pair

Capability:

[x] Bitswap enable (checked)
[ ] SRA enable

Test mode (radio buttons):

(o) Normal
( ) Reverb
( ) Medley
( ) No retrain
( ) L3

Then, there's a screen with "Tone selection" with all "upstream tones" and all "downstream tones" selected.
 
From the "Diagnostics" page on the Tenda router:

Test your ENET0 Connection: PASS
Test your USB Connection: DOWN
Test the connection to your DSL service provider

Test ADSL Synchronization: PASS
Test ATM OAM F5 segment ping: FAIL
Test ATM OAM F5 end-to-end ping: FAIL
Test the connection to your Internet service provider

Test PPP server connection: PASS
Test authentication with ISP: PASS
Test the assigned IP address: PASS
Ping default gateway: PASS
Ping primary Domain Name Server: PASS
 
All of that seems good!

I think twhitehead has hit the nail on the head with regards to IPv6. Try disabling all the IPv6 protocols on all your machines when using the Tenda modem.
 
Pada said:
I think twhitehead has hit the nail on the head with regards to IPv6. Try disabling all the IPv6 protocols on all your machines when using the Tenda modem.
Click to expand...

Just solved it, but it has nothing to do with IPv6, but as per my last hunch, the MTU settings of the network device on the other end of the cable connected to the Tenda's ethernet port (the PC/server/router's ethernet port setting).

So, I manually set the MTU of my PC's ethernet port to 1492, matching the ADSL router's WAN port MTU setting. The PC's ethernet port's MTU was previously on auto, which configured it at 1500.

However, what is still perplexing is that the auto setting for the MTU works when connecting to the Netgear router, but not the Tenda router. This must have something to do with whether, or not the Tenda router's ethernet drivers negotiate the MTU setting with the other end?!? I will try find out why.

Thanks for all the previous suggestions!

I'll post a new specific thread for this issue, with the solution, for others to find more easily.

http://mybroadband.co.za/vb/showthr...ettings-to-work-with-Tenda-D820R-Adsl2-router
 
Last edited:
You must log in or register to reply here.
Back
Top
Sign up to the MyBroadband newsletter
X