Network is blocked till ping is issued

Network is blocked till ping is issued

[DI BACCO ANTONIO - technolabs]

I have two hosts 100.1.0.1 (NotLinux) and 100.1.0.2 (linux-2.6.19.2) on
a vlan.
On the linux box the vlan interface is created with vconfig and is
attached to a Virtual PHY (fixed PHY).
When Linux box starts up, NotLinux wants to setup a TCP connection with
"Linux box" and sends a SYN packet receiving no answer from "Linux box".
If from the console of "Linux box" I issue a ping to NotLinux then,
after a while, the linux box starts responding to Windows.

Bye,
Antonio.

Re: Network is blocked till ping is issued(update)

[DI BACCO ANTONIO - technolabs]

I have two hosts 100.1.0.1 (NotLinux) and 100.1.0.2 (linux-2.6.19.2 on
MPC880) on
a vlan.
On the linux box the vlan interface is created with vconfig on the eth1
and is
attached to a Virtual PHY (fixed PHY).
When Linux box starts up, NotLinux wants to setup a TCP connection with
"Linux box" and sends a SYN packet receiving no answer from "Linux box".
If from the console of "Linux box" I issue a ping to NotLinux then,
after a while, the linux box starts responding to Windows.

Bye,
Antonio.

Re: Network is blocked till ping is issued

[Florian A. Voegel]

Hi Antonio,

sounds to me like it could be a classical ARP problem. Have you checked the ARP cache on the non-Linux machine?

On Wed, 29 Aug 2007 19:27:19 +0200
"DI BACCO ANTONIO - technolabs" <Antonio.DiBacco@technolabs.it> wrote:

> I have two hosts 100.1.0.1 (NotLinux) and 100.1.0.2 (linux-2.6.19.2) on
> a vlan.
> On the linux box the vlan interface is created with vconfig and is
> attached to a Virtual PHY (fixed PHY).
> When Linux box starts up, NotLinux wants to setup a TCP connection with
> "Linux box" and sends a SYN packet receiving no answer from "Linux box".
> If from the console of "Linux box" I issue a ping to NotLinux then,
> after a while, the linux box starts responding to Windows.
> 
> Bye,
> Antonio.
> 
> _______________________________________________
> Linuxppc-embedded mailing list
> Linuxppc-embedded@ozlabs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-embedded
> 

RE: Network is blocked till ping is issued

[DI BACCO ANTONIO - technolabs]

> sounds to me like it could be a classical ARP problem. Have you
checked the ARP cache on the non-Linux
> machine?

But if Linux received the SYN packet of TCP connection, shouldn't the
Linux machine reply to the source mac address of SYN packet with a
SYN,ACK packet?

Re: Network is blocked till ping is issued

[Andy Gospodarek]

On 8/30/07, DI BACCO ANTONIO - technolabs <Antonio.DiBacco@technolabs.it> wrote:
> > sounds to me like it could be a classical ARP problem. Have you
> checked the ARP cache on the non-Linux
> > machine?
>
> But if Linux received the SYN packet of TCP connection, shouldn't the
> Linux machine reply to the source mac address of SYN packet with a
> SYN,ACK packet?
>

No.  You are confusing Ethernet frames and IP packets a little bit.
If a Linux machine receives a SYN from a remote host (not on the same
network) then the Linux machine needs to ARP for the router that is
listed as the default route in the routing table.

If no such default route exists, you will not be able to reach the
remote host.  If the router doesn't reply to your ARP request, you
will not be able to reach the remote host.

Check to make sure you are not having either one of these problems.

RE: Network is blocked till ping is issued

[DI BACCO ANTONIO - technolabs]

>No.  You are confusing Ethernet frames and IP packets a little bit.
>If a Linux machine receives a SYN from a remote host (not on the same
>network) then the Linux machine needs to ARP for the router that is
>listed as the default route in the routing table.

>If no such default route exists, you will not be able to reach the
>remote host.  If the router doesn't reply to your ARP request, you
>will not be able to reach the remote host.

>Check to make sure you are not having either one of these problems.

I'm on the same network: NotLinux is 100.1.0.1 and Linux is 100.1.0.2
with netmask 255.255.255.0

Thank you,
Antonio.