<p>When using a self hosted kubeadm in ubuntu, I could not access other pods and external network from within k8s pod but am able to access using regular docker containers.</p>

<p>I tried with different types of pod network including calico, weave and flannel.</p>

<p>I followed the debugging instructinos from <a href="https://kubernetes.io/docs/concepts/services-networking/dns-pod-service/" rel="nofollow noreferrer">here</a> without any success, below is the logs.</p>

<pre><code>$ kubectl exec -ti busybox -- nslookup kubernetes.default
Server:    10.96.0.10
Address 1: 10.96.0.10

nslookup: can't resolve 'kubernetes.default'


$ kubectl exec busybox cat /etc/resolv.conf
nameserver 10.96.0.10
search default.svc.cluster.local svc.cluster.local cluster.local
options ndots:5


$ kubectl get pods --namespace=kube-system -l k8s-app=kube-dns
NAME                        READY     STATUS    RESTARTS   AGE
kube-dns-2425271678-9zwtd   3/3       Running   0          12m


$ kubectl logs --namespace=kube-system $(kubectl get pods --namespace=kube-system -l k8s-app=kube-dns -o name) -c kubedns
I0823 16:02:58.407162       6 dns.go:48] version: 1.14.3-4-gee838f6
I0823 16:02:58.408957       6 server.go:70] Using configuration read from directory: /kube-dns-config with period 10s
I0823 16:02:58.409223       6 server.go:113] FLAG: --alsologtostderr="false"
I0823 16:02:58.409248       6 server.go:113] FLAG: --config-dir="/kube-dns-config"
I0823 16:02:58.409288       6 server.go:113] FLAG: --config-map=""
I0823 16:02:58.409301       6 server.go:113] FLAG: --config-map-namespace="kube-system"
I0823 16:02:58.409309       6 server.go:113] FLAG: --config-period="10s"
I0823 16:02:58.409325       6 server.go:113] FLAG: --dns-bind-address="0.0.0.0"
I0823 16:02:58.409333       6 server.go:113] FLAG: --dns-port="10053"
I0823 16:02:58.409370       6 server.go:113] FLAG: --domain="cluster.local."
I0823 16:02:58.409387       6 server.go:113] FLAG: --federations=""
I0823 16:02:58.409401       6 server.go:113] FLAG: --healthz-port="8081"
I0823 16:02:58.409411       6 server.go:113] FLAG: --initial-sync-timeout="1m0s"
I0823 16:02:58.409434       6 server.go:113] FLAG: --kube-master-url=""
I0823 16:02:58.409451       6 server.go:113] FLAG: --kubecfg-file=""
I0823 16:02:58.409458       6 server.go:113] FLAG: --log-backtrace-at=":0"
I0823 16:02:58.409470       6 server.go:113] FLAG: --log-dir=""
I0823 16:02:58.409478       6 server.go:113] FLAG: --log-flush-frequency="5s"
I0823 16:02:58.409489       6 server.go:113] FLAG: --logtostderr="true"
I0823 16:02:58.409496       6 server.go:113] FLAG: --nameservers=""
I0823 16:02:58.409521       6 server.go:113] FLAG: --stderrthreshold="2"
I0823 16:02:58.409533       6 server.go:113] FLAG: --v="2"
I0823 16:02:58.409544       6 server.go:113] FLAG: --version="false"
I0823 16:02:58.409559       6 server.go:113] FLAG: --vmodule=""
I0823 16:02:58.409728       6 server.go:176] Starting SkyDNS server (0.0.0.0:10053)
I0823 16:02:58.467505       6 server.go:198] Skydns metrics enabled (/metrics:10055)
I0823 16:02:58.467640       6 dns.go:147] Starting endpointsController
I0823 16:02:58.467810       6 dns.go:150] Starting serviceController
I0823 16:02:58.557166       6 logs.go:41] skydns: ready for queries on cluster.local. for tcp://0.0.0.0:10053 [rcache 0]
I0823 16:02:58.557335       6 logs.go:41] skydns: ready for queries on cluster.local. for udp://0.0.0.0:10053 [rcache 0]
I0823 16:02:58.968454       6 dns.go:174] Waiting for services and endpoints to be initialized from apiserver...
I0823 16:02:59.468406       6 dns.go:171] Initialized services and endpoints from apiserver
I0823 16:02:59.468698       6 server.go:129] Setting up Healthz Handler (/readiness)
I0823 16:02:59.469064       6 server.go:134] Setting up cache handler (/cache)
I0823 16:02:59.469305       6 server.go:120] Status HTTP port 8081


$ kubectl logs --namespace=kube-system $(kubectl get pods --namespace=kube-system -l k8s-app=kube-dns -o name) -c dnsmasq
I0823 16:02:59.445525      11 main.go:76] opts: {{/usr/sbin/dnsmasq [-k --cache-size=1000 --log-facility=- --server=/cluster.local/127.0.0.1#10053 --server=/in-addr.arpa/127.0.0.1#10053 --server=/ip6.arpa/127.0.0.1#10053] true} /etc/k8s/dns/dnsmasq-nanny 10000000000}
I0823 16:02:59.445741      11 nanny.go:86] Starting dnsmasq [-k --cache-size=1000 --log-facility=- --server=/cluster.local/127.0.0.1#10053 --server=/in-addr.arpa/127.0.0.1#10053 --server=/ip6.arpa/127.0.0.1#10053]
I0823 16:02:59.820424      11 nanny.go:108] dnsmasq[38]: started, version 2.76 cachesize 1000
I0823 16:02:59.820546      11 nanny.go:108] dnsmasq[38]: compile time options: IPv6 GNU-getopt no-DBus no-i18n no-IDN DHCP DHCPv6 no-Lua TFTP no-conntrack ipset auth no-DNSSEC loop-detect inotify
I0823 16:02:59.820596      11 nanny.go:108] dnsmasq[38]: using nameserver 127.0.0.1#10053 for domain ip6.arpa 
I0823 16:02:59.820623      11 nanny.go:108] dnsmasq[38]: using nameserver 127.0.0.1#10053 for domain in-addr.arpa 
I0823 16:02:59.820659      11 nanny.go:108] dnsmasq[38]: using nameserver 127.0.0.1#10053 for domain cluster.local 
I0823 16:02:59.820736      11 nanny.go:108] dnsmasq[38]: reading /etc/resolv.conf
I0823 16:02:59.820762      11 nanny.go:108] dnsmasq[38]: using nameserver 127.0.0.1#10053 for domain ip6.arpa 
I0823 16:02:59.820788      11 nanny.go:108] dnsmasq[38]: using nameserver 127.0.0.1#10053 for domain in-addr.arpa 
I0823 16:02:59.820825      11 nanny.go:108] dnsmasq[38]: using nameserver 127.0.0.1#10053 for domain cluster.local 
I0823 16:02:59.820850      11 nanny.go:108] dnsmasq[38]: using nameserver 8.8.8.8#53
I0823 16:02:59.820928      11 nanny.go:108] dnsmasq[38]: read /etc/hosts - 7 addresses
I0823 16:02:59.821193      11 nanny.go:111] 
W0823 16:02:59.821212      11 nanny.go:112] Got EOF from stdout

$ kubectl logs --namespace=kube-system $(kubectl get pods --namespace=kube-system -l k8s-app=kube-dns -o name) -c sidecar
ERROR: logging before flag.Parse: I0823 16:03:00.789793      26 main.go:48] Version v1.14.3-4-gee838f6
ERROR: logging before flag.Parse: I0823 16:03:00.790052      26 server.go:45] Starting server (options {DnsMasqPort:53 DnsMasqAddr:127.0.0.1 DnsMasqPollIntervalMs:5000 Probes:[{Label:kubedns Server:127.0.0.1:10053 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:1} {Label:dnsmasq Server:127.0.0.1:53 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:1}] PrometheusAddr:0.0.0.0 PrometheusPort:10054 PrometheusPath:/metrics PrometheusNamespace:kubedns})
ERROR: logging before flag.Parse: I0823 16:03:00.790121      26 dnsprobe.go:75] Starting dnsProbe {Label:kubedns Server:127.0.0.1:10053 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:1}
ERROR: logging before flag.Parse: I0823 16:03:00.790419      26 dnsprobe.go:75] Starting dnsProbe {Label:dnsmasq Server:127.0.0.1:53 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:1}
</code></pre>

<p>Below is the etc/resolv.conf from the master.</p>

<pre><code>$ cat /etc/resolv.conf
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 8.8.8.8

$ kubeadm version
kubeadm version: &amp;version.Info{Major:"1", Minor:"7", GitVersion:"v1.7.3", GitCommit:"2c2fe6e8278a5db2d15a013987b53968c743f2a1", GitTreeState:"clean", BuildDate:"2017-08-03T06:43:48Z", GoVersion:"go1.8.3", Compiler:"gc", Platform:"linux/amd64"}
</code></pre>

<p>Below is the etc/resolv.conf from worker node where the pod is running</p>

<pre><code># Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 8.8.4.4
nameserver 8.8.8.
</code></pre>

<p>Here is the output of sudo iptables -n -L</p>

<pre><code>Chain INPUT (policy ACCEPT)
target     prot opt source               destination         
cali-INPUT  all  --  0.0.0.0/0            0.0.0.0/0            /* cali:Cz_u1IQiXIMmKD4c */
KUBE-SERVICES  all  --  0.0.0.0/0            0.0.0.0/0            /* kubernetes service portals */
KUBE-FIREWALL  all  --  0.0.0.0/0            0.0.0.0/0           

Chain FORWARD (policy DROP)
target     prot opt source               destination         
cali-FORWARD  all  --  0.0.0.0/0            0.0.0.0/0            /* cali:wUHhoiAYhphO9Mso */
DOCKER-USER  all  --  0.0.0.0/0            0.0.0.0/0           
DOCKER-ISOLATION  all  --  0.0.0.0/0            0.0.0.0/0           
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0            ctstate RELATED,ESTABLISHED
DOCKER     all  --  0.0.0.0/0            0.0.0.0/0           
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0           
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0           
WEAVE-NPC  all  --  0.0.0.0/0            0.0.0.0/0           
NFLOG      all  --  0.0.0.0/0            0.0.0.0/0            state NEW nflog-group 86
DROP       all  --  0.0.0.0/0            0.0.0.0/0           
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0           
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0            ctstate RELATED,ESTABLISHED

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination         
cali-OUTPUT  all  --  0.0.0.0/0            0.0.0.0/0            /* cali:tVnHkvAo15HuiPy0 */
KUBE-SERVICES  all  --  0.0.0.0/0            0.0.0.0/0            /* kubernetes service portals */
KUBE-FIREWALL  all  --  0.0.0.0/0            0.0.0.0/0           

Chain DOCKER (1 references)
target     prot opt source               destination         

Chain DOCKER-ISOLATION (1 references)
target     prot opt source               destination         
RETURN     all  --  0.0.0.0/0            0.0.0.0/0           

Chain DOCKER-USER (1 references)
target     prot opt source               destination         
RETURN     all  --  0.0.0.0/0            0.0.0.0/0           

Chain KUBE-FIREWALL (2 references)
target     prot opt source               destination         
DROP       all  --  0.0.0.0/0            0.0.0.0/0            /* kubernetes firewall for dropping marked packets */ mark match 0x8000/0x8000

Chain KUBE-SERVICES (2 references)
target     prot opt source               destination         
REJECT     tcp  --  0.0.0.0/0            10.96.252.131        /* default/redis-cache-service:redis has no endpoints */ tcp dpt:6379 reject-with icmp-port-unreachable
REJECT     tcp  --  0.0.0.0/0            10.96.252.131        /* default/redis-cache-service:cluster has no endpoints */ tcp dpt:16379 reject-with icmp-port-unreachable
REJECT     tcp  --  0.0.0.0/0            10.105.180.126       /* default/redis-pubsub-service:redis has no endpoints */ tcp dpt:6379 reject-with icmp-port-unreachable
REJECT     tcp  --  0.0.0.0/0            10.105.180.126       /* default/redis-pubsub-service:cluster has no endpoints */ tcp dpt:16379 reject-with icmp-port-unreachable

Chain WEAVE-NPC (1 references)
target     prot opt source               destination         
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0            state RELATED,ESTABLISHED
ACCEPT     all  --  0.0.0.0/0            224.0.0.0/4         
WEAVE-NPC-DEFAULT  all  --  0.0.0.0/0            0.0.0.0/0            state NEW
WEAVE-NPC-INGRESS  all  --  0.0.0.0/0            0.0.0.0/0            state NEW
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0            ! match-set weave-local-pods dst

Chain WEAVE-NPC-DEFAULT (1 references)
target     prot opt source               destination         
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0            match-set weave-k?Z;25^M}|1s7P3|H9i;*;MhG dst
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0            match-set weave-iuZcey(5DeXbzgRFs8Szo]+@p dst
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0            match-set weave-4vtqMI+kx/2]jD%_c0S%thO%V dst

Chain WEAVE-NPC-INGRESS (1 references)
target     prot opt source               destination         

Chain cali-FORWARD (1 references)
target     prot opt source               destination         
cali-from-wl-dispatch  all  --  0.0.0.0/0            0.0.0.0/0            /* cali:X3vB2lGcBrfkYquC */
cali-to-wl-dispatch  all  --  0.0.0.0/0            0.0.0.0/0            /* cali:UtJ9FnhBnFbyQMvU */
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0            /* cali:Tt19HcSdA5YIGSsw */
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0            /* cali:9LzfFCvnpC5_MYXm */
MARK       all  --  0.0.0.0/0            0.0.0.0/0            /* cali:7AofLLOqCM5j36rM */ MARK and 0xf1ffffff
cali-from-host-endpoint  all  --  0.0.0.0/0            0.0.0.0/0            /* cali:QM1_joSl7tL76Az7 */ mark match 0x0/0x1000000
cali-to-host-endpoint  all  --  0.0.0.0/0            0.0.0.0/0            /* cali:C1QSog3bk0AykjAO */
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0            /* cali:DmFiPAmzcisqZcvo */ /* Host endpoint policy accepted packet. */ mark match 0x1000000/0x1000000

Chain cali-INPUT (1 references)
target     prot opt source               destination         
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0            /* cali:i7okJZpS8VxaJB3n */ mark match 0x1000000/0x1000000
DROP       4    --  0.0.0.0/0            0.0.0.0/0            /* cali:p8Wwvr6qydjU36AQ */ /* Drop IPIP packets from non-Calico hosts */ ! match-set cali4-all-hosts src
cali-wl-to-host  all  --  0.0.0.0/0            0.0.0.0/0           [goto]  /* cali:QZT4Ptg57_76nGng */
MARK       all  --  0.0.0.0/0            0.0.0.0/0            /* cali:V0Veitpvpl5h1xwi */ MARK and 0xf0ffffff
cali-from-host-endpoint  all  --  0.0.0.0/0            0.0.0.0/0            /* cali:3R1g0cpvSoBlKzVr */
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0            /* cali:efXx-pqD4s60WsDL */ /* Host endpoint policy accepted packet. */ mark match 0x1000000/0x1000000

Chain cali-OUTPUT (1 references)
target     prot opt source               destination         
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0            /* cali:YQSSJIsRcHjFbXaI */ mark match 0x1000000/0x1000000
RETURN     all  --  0.0.0.0/0            0.0.0.0/0            /* cali:KRjBsKsBcFBYKCEw */
MARK       all  --  0.0.0.0/0            0.0.0.0/0            /* cali:3VKAQBcyUUW5kS_j */ MARK and 0xf0ffffff
cali-to-host-endpoint  all  --  0.0.0.0/0            0.0.0.0/0            /* cali:Z1mBCSH1XHM6qq0k */
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0            /* cali:N0jyWt2RfBedKw3L */ /* Host endpoint policy accepted packet. */ mark match 0x1000000/0x1000000

Chain cali-failsafe-in (0 references)
target     prot opt source               destination         
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0            /* cali:wWFQM43tJU7wwnFZ */ multiport dports 22
ACCEPT     udp  --  0.0.0.0/0            0.0.0.0/0            /* cali:LwNV--R8MjeUYacw */ multiport dports 68

Chain cali-failsafe-out (0 references)
target     prot opt source               destination         
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0            /* cali:73bZKoyDfOpFwC2T */ multiport dports 2379
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0            /* cali:QMFuWo6o-d9yOpNm */ multiport dports 2380
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0            /* cali:Kup7QkrsdmfGX0uL */ multiport dports 4001
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0            /* cali:xYYr5PEqDf_Pqfkv */ multiport dports 7001
ACCEPT     udp  --  0.0.0.0/0            0.0.0.0/0            /* cali:nbWBvu4OtudVY60Q */ multiport dports 53
ACCEPT     udp  --  0.0.0.0/0            0.0.0.0/0            /* cali:UxFu5cDK5En6dT3Y */ multiport dports 67

Chain cali-from-host-endpoint (2 references)
target     prot opt source               destination         

Chain cali-from-wl-dispatch (2 references)
target     prot opt source               destination         
DROP       all  --  0.0.0.0/0            0.0.0.0/0            /* cali:zTj6P0TIgYvgz-md */ /* Unknown interface */

Chain cali-to-host-endpoint (2 references)
target     prot opt source               destination         

Chain cali-to-wl-dispatch (1 references)
target     prot opt source               destination         
DROP       all  --  0.0.0.0/0            0.0.0.0/0            /* cali:7KNphB1nNHw80nIO */ /* Unknown interface */

Chain cali-wl-to-host (1 references)
target     prot opt source               destination         
ACCEPT     udp  --  0.0.0.0/0            0.0.0.0/0            /* cali:aEOMPPLgak2S0Lxs */ multiport sports 68 multiport dports 67
ACCEPT     udp  --  0.0.0.0/0            0.0.0.0/0            /* cali:SzR8ejPiuXtFMS8B */ multiport dports 53
cali-from-wl-dispatch  all  --  0.0.0.0/0            0.0.0.0/0            /* cali:MEmlbCdco0Fefcrw */
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0            /* cali:LZBoXHDOlr3ok4R3 */ /* Configured DefaultEndpointToHostAction */
</code></pre>

<p>Maybe it is your iptable has old record ,because i think you use kubeadm reset or setting maybe overlay network before,
Please do this thing after kubeadm reset and remove docker </p>

<p>check your ip link
<code>
ip link
</code>
and clean the old record</p>

<p><code>
ip link delete cni0
ip link delete flannel.1
</code>
(if there are other network e.g weave, please delete it)</p>

<p>then clean the iptalbes</p>

<p><code>
iptables -P INPUT ACCEPT
iptables -P FORWARD ACCEPT
iptables -P OUTPUT ACCEPT
iptables -t nat -F
iptables -t mangle -F
iptables -F
iptables -X
</code></p>

<p>then reinstall docker and kubernetes, that the pod should can get the 
external network </p>

<p>Good Luck!</p>
