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Topic: Block DHCP over bridge?

The content of this topic has been archived on 1 May 2018. There are no obvious gaps in this topic, but there may still be some posts missing at the end.

Hello, I'm trying to set-up a wireless bridge using two wrt54g routers.  However, each side has it's own internet connection, and a separate wrt54g doing the NAT for it.  I want to block DHCP traffic over the bridge.  Anyone know a way to block dhcp traffic over the bridge?

Search the forums and wiki for 'ebtables'.

spent about 12 hours on this.  11 hours of those spend on the forum and wiki.  Anything that actually talks about HOW to do it is out of date.  Anything recent is geared toward someone that knows how to use ebtables...

I have ebatbles loaded, I think this is what I need to make it all work;

ebtables -A INPUT --ip-destination-port 67:68 -j DROP                   

but it comes back with;
For IP filtering the protocol must be specified as IPv4.

so I add that;

root@OpenWrt:/etc# ebtables -A INPUT --ip-protocol IPv4 --ip-destination-port 67:68 -j DROP
Unknown specified IP protocol - IPv4.

Then I tried this;
root@OpenWrt:/etc# ebtables -A FORWARD -p ipv4 --ip-protocol udp --ip-destination-port 67:68 -j DROP
Problem with the specified protocol.

(Last edited by logandzwon on 18 Jul 2006, 08:33)

OK, I belive these are the correct commands for what I'm trying to do;

$EBTABLES -A INPUT --in-interface $PUB --protocol IPv4 --ip-protocol udp --ip-source-port 68 -j DROP
$EBTABLES -A INPUT --in-interface $PUB --protocol IPv4 --ip-protocol udp --ip-destination-port 67 -j DROP
$EBTABLES -A FORWARD --in-interface $PRIV --protocol IPv4 --ip-protocol udp --ip-source-port 68 -j DROP
$EBTABLES -A FORWARD --in-interface $PUB --protocol IPv4 --ip-protocol udp --ip-destination-port 67 -j DROP

but they still say;
Problem with the specified protocol.

Is the ebtables possibly broken in openwrt rc5?

(Last edited by logandzwon on 18 Jul 2006, 09:01)

found the issue, the ebtables package is missing the /etc/ethertypes

then made the lines;
ebtables -A INPUT --in-interface vlan0 --protocol ipv4 --ip-protocol udp --ip-source-port 67:68 -j DROP
ebtables -A INPUT --in-interface vlan0 --protocol ipv4 --ip-protocol udp --ip-destination-port 67:68 -j DROP
ebtables -A FORWARD --in-interface vlan0 --protocol ipv4 --ip-protocol udp --ip-destination-port 67:68 -j DROP
ebtables -A FORWARD --in-interface vlan0 --protocol ipv4 --ip-protocol udp --ip-source-port 67:68 -j DROP

(Last edited by logandzwon on 18 Jul 2006, 09:42)

If you can update the wiki with your findings, that would be very useful to others.

I had the same problem, /etc/ethertypes is missing. If you need to use ebtables copy/paste this at the command line:

cat << EOF > /etc/ethertypes
# Ethernet frame types
#               This file describes some of the various Ethernet
#               protocol types that are used on Ethernet networks.
# This list could be found on:
# <name>    <hexnumber> <alias1>...<alias35> #Comment
IPv4            0800    ip ip4          # Internet IP (IPv4)
X25             0805
ARP             0806    ether-arp       #
FR_ARP          0808                    # Frame Relay ARP        [RFC1701]
BPQ             08FF                    # G8BPQ AX.25 Ethernet Packet
DEC             6000                    # DEC Assigned proto
DNA_DL          6001                    # DEC DNA Dump/Load
DNA_RC          6002                    # DEC DNA Remote Console
DNA_RT          6003                    # DEC DNA Routing
LAT             6004                    # DEC LAT
DIAG            6005                    # DEC Diagnostics
CUST            6006                    # DEC Customer use
SCA             6007                    # DEC Systems Comms Arch
TEB             6558                    # Trans Ether Bridging   [RFC1701]
RAW_FR          6559                    # Raw Frame Relay        [RFC1701]
AARP            80F3                    # Appletalk AARP
ATALK           809B                    # Appletalk
802_1Q          8100    8021q 1q 802.1q dot1q # 802.1Q Virtual LAN tagged frame
IPX             8137                    # Novell IPX
NetBEUI         8191                    # NetBEUI
IPv6            86DD    ip6             # IP version 6
PPP             880B                    # PPP
ATMMPOA         884C                    # MultiProtocol over ATM
PPP_DISC        8863                    # PPPoE discovery messages
PPP_SES         8864                    # PPPoE session messages
ATMFATE         8884                    # Frame-based ATM Transport over Ethernet
LOOP            9000    loopback        # loop proto

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