Problem using -p udp

[Phil Sutter <phil@ctekproducts.com>]

Hi,

I have been using Iptables on linux 2.4.26 for several years. I am
running on an Axis platform (cris architecture). Recently I started
moving my application to 2.6.19 and am using iptables 1.3.7. When I try
to use the sample rules shown below from my old environment, they fail
with an invalid parameter. The parameter causing the issue is the "udp"
associated with the "-p".  If I issue the same rule with a "-p tcp" they
work fine. Could someone explain why  "-p udp"  will not work?

/sbin/iptables -t nat -A PREROUTING -i ppp0 -p udp --dport 80 -j
REDIRECT --to-port 6383

/sbin/iptables -t nat -A PREROUTING -i ppp0 -p udp --dport 90 -j DNAT
--to 192.168.1.122:80


Thank you,

Phil