[ipxe-devel] iSCSI boot from SAN issue w/ iPXE Equallogic and vlan

Thomas Pöhler tp at turtle-entertainment.de
Wed Jun 19 12:27:42 UTC 2013

Hey Michael,

thanks for your help. that is exactly what we found out yesterday an hour
before your mail :)

tl;dr for everyone who tries to boot from a tagged vlan:
the undi driver is not capable of handling packets with a frame size
greater than 1514. Since the vlan tag is added on top, this could exceed
maximal frame size if you have payload. In case of arp or dhcp request this
often works because the payload is too small to fill up the whole frame.

Solution: use ipxe.kpxe instead of undionly.kpxe. This should include the
drivers for your network card which are then able to handle packets with
vlan tag.

make bin/ipxe.kpxe EMBED=yourscript_which_creates_vlan < that should do it

make sure your initramfs then also creates the vlan. you need to hook in
iscsi_tcp the 8021q module and a script which creates the vlan with vconfig.

Thanks to everybody for your help!
If anyone has question, feel free to contact me.

2013/6/18 Michael Brown <mbrown at fensystems.co.uk>

> On Monday 17 Jun 2013 11:17:24 Thomas Pöhler wrote:
> > Therefore we are using our standard NIC with PXE booting undionly.kpxe
> > which then logs in the disk to boot.
> >
> > Without a tagged vlan this is working flawless. When we try to boot it
> over
> > a tagged vlan the following happens:
> Most likely cause is that the underlying UNDI driver configures the NIC
> for a
> frame size of 1514 bytes, which doesn't allow enough space for the 4-byte
> header.  Shorter packets will be received OK, but as soon as you try to
> read a
> maximum-length packet (i.e. as soon as grub starts reading multiple sectors
> per request) then the NIC will appear to stop receiving.
> To use VLANs, your best option is probably to try using a native iPXE
> driver
> (ipxe.pxe rather than undionly.kpxe).
> Michael

Turtle Entertainment GmbH
Thomas Pöhler, Director IT
Siegburger Str. 189
50679 Cologne
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