WLAN client -> WLAN client ping yields no "echo reply"

Question

My WLAN clients are connected to an AT&T U-Verse Arris NVG589. When I try and ping my Mac on my home WLAN, I don’t get a response.

tcpdump 'icmp[icmptype] = icmp-echo or icmp[icmptype] = icmp-echoreply'
tcpdump: data link type PKTAP
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on pktap, link-type PKTAP (Packet Tap), capture size 262144 bytes

A ping from this Mac to www.google.com works:

21:46:20.817743 IP work-mbp.attlocal.net > yv-in-f103.1e100.net: ICMP echo request, id 55595, seq 0, length 64
21:46:20.842309 IP yv-in-f103.1e100.net > work-mbp.attlocal.net: ICMP echo reply, id 55595, seq 0, length 64
21:46:21.820431 IP work-mbp.attlocal.net > yv-in-f103.1e100.net: ICMP echo request, id 55595, seq 1, length 64
21:46:21.844247 IP yv-in-f103.1e100.net > work-mbp.attlocal.net: ICMP echo reply, id 55595, seq 1, length 64

A ping from one Mac to another on the WLAN shows no "echo reply":

21:34:34.994444 IP homempb.attlocal.net > work-mbp.attlocal.net: ICMP echo request, id 12, seq 0, length 16
21:34:35.989923 IP homempb.attlocal.net > work-mbp.attlocal.net: ICMP echo request, id 12, seq 1, length 16
21:34:37.978274 IP homempb.attlocal.net > work-mbp.attlocal.net: ICMP echo request, id 12, seq 2, length 16
21:34:40.213181 IP homempb.attlocal.net > work-mbp.attlocal.net: ICMP echo request, id 12, seq 3, length 16
21:34:41.978188 IP homempb.attlocal.net > work-mbp.attlocal.net: ICMP echo request, id 12, seq 4, length 16
21:34:43.978284 IP homempb.attlocal.net > work-mbp.attlocal.net: ICMP echo request, id 12, seq 5, length 16

El Capitan firewall is disabled.

Answer 1

Turns out the packet filter was enabled and only allowing internet bound ping:

pfctl -a '*' -s rules

showed this rule:

pass out inet proto icmp all keep state

I temporarily disabled the packet filter using:

pfctl -d 

and the ping "echo reply" started showing up.