This article provides information on how to set the MTU on an aggregated interface.
For example, when setting the MTU to 9000 on two ports, which are linked to ae0 , the ae child device mtu setting is not allowed message is noticed.
To set the MTU on an aggregated interface:
#set interfaces ae0 mtu 9000 #commit
#run show interfaces ae0 extensive Physical interface: ae0, Enabled, Physical link is Down Interface index: 151, SNMP ifIndex: 546, Generation: 154 Link-level type: Ethernet, MTU: 9000, Speed: Unspecified, BPDU Error: None, MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: Disabled, Flow control: Disabled, Minimum links needed: 1, Minimum bandwidth needed: 0 Device flags : Present Running Interface flags: Hardware-Down SNMP-Traps Internal: 0x4000 Current address: 02:00:00:00:00:fc, Hardware address: 02:00:00:00:00:fc Last flapped : 2011-11-22 01:09:02 UTC (00:37:43 ago) Statistics last cleared: Never Traffic statistics: Input bytes : 0 0 bps Output bytes : 0 0 bps Input packets: 0 0 pps Output packets: 0 0 pps Input errors: Errors: 0, Drops: 0, Framing errors: 0, Runts: 0, Giants: 0, Policed discards: 0, Resource errors: 0 Output errors: Carrier transitions: 0, Errors: 0, Drops: 0, MTU errors: 0, Resource errors: 0