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DHCP on management (eth4) and public VLAN (eth4.3281) breaks router

[ Edited ]

I am having trouble with an ERX at a client where I want to run DHCP on eth4 and eth4.3281 interfaces.  Straight out of the box, if I configure the VLAN interface and eth4 with DHCP and configure a masquerade rule to use either eth4 or eth4.3281 there is no connectivity through the device.  As soon as I remove the "DHCP" option on either interface (and set the masq rule to the "up" interface) I get connectivity through the device.

 

Have I just forgotten something I used to know or is this not possible?  I was pretty certain I've done this at other clients but I can't recall now.  I'll start digging through our clients to find who might be running a setup like this.

 

Edit: Oh yeah, 1.10.8 firmware

 


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Re: DHCP on management (eth4) and public VLAN (eth4.3281) breaks router

How should the router know where to route what as long as you do not configure load balancing or some routing protocol?

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Established Member
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Re: DHCP on management (eth4) and public VLAN (eth4.3281) breaks router

Here is the config.  As basic as I can get it and it's still breaking with both interfaces on DHCP.

 

interfaces {
    ethernet eth0 {
        address 192.168.1.1/24
        duplex auto
        speed auto
    }
    ethernet eth1 {
        address dhcp
        duplex auto
        speed auto
    }
    ethernet eth2 {
        duplex auto
        speed auto
    }
    ethernet eth3 {
        duplex auto
        speed auto
    }
    ethernet eth4 {
        address dhcp
        duplex auto
        poe {
            output off
        }
        speed auto
        vif 3281 {
            address dhcp
            description "Public VLAN"
            mtu 1500
        }
    }
    loopback lo {
    }
    switch switch0 {
        mtu 1500
    }
}
service {
    gui {
        http-port 80
        https-port 443
        older-ciphers enable
    }
    nat {
        rule 5000 {
            description masquerade
            log disable
            outbound-interface eth4
            protocol all
            type masquerade
        }
    }
    ssh {
        port 22
        protocol-version v2
    }
}
system {
    host-name ubnt
    login {
        user ubnt {
            authentication {
                encrypted-password $1$zKNoUbAo$gomzUbYvgyUMcD436Wo66.
            }
            level admin
        }
    }
    ntp {
        server 0.ubnt.pool.ntp.org {
        }
        server 1.ubnt.pool.ntp.org {
        }
        server 2.ubnt.pool.ntp.org {
        }
        server 3.ubnt.pool.ntp.org {
        }
    }
    syslog {
        global {
            facility all {
                level notice
            }
            facility protocols {
                level debug
            }
        }
    }
    time-zone UTC
}


/* Warning: Do not remove the following line. */
/* === vyatta-config-version: "config-management@1:conntrack@1:cron@1:dhcp-relay@1:dhcp-server@4:firewall@5:ipsec@5:nat@3:qos@1:quagga@2:suspend@1:system@4:ubnt-pptp@1:ubnt-udapi-server@1:ubnt-unms@1:ubnt-util@1:vrrp@1:webgui@1:webproxy@1:zone-policy@1" === */
/* Release version: v1.10.8.5142457.181120.1809 */
Established Member
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Re: DHCP on management (eth4) and public VLAN (eth4.3281) breaks router

Out  Maybe this is a known issue?  I didn't search much...

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Re: DHCP on management (eth4) and public VLAN (eth4.3281) breaks router

Ok, I figured it out.  When I use DHCP on both interfaces it inserts 2 default routes into the routing table with equal administrative distances.

 

I don't know if that is expected behaviour or not but it's broken behaviour.

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Re: DHCP on management (eth4) and public VLAN (eth4.3281) breaks router

How should the router know where to route what as long as you do not configure load balancing or some routing protocol?
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Re: DHCP on management (eth4) and public VLAN (eth4.3281) breaks router


@Alestrix wrote:
How should the router know where to route what as long as you do not configure load balancing or some routing protocol?

I was coming to the same conclusion.